new words

New words
abbreviate-товчлох, хураангуйлах, богиносгох
action-ажил хэрэг, үйл ажиллагаа
activity-идэвх, үйл ажиллагаа
affect-нөлөөлөх, хөндөх
ahead-урагшаа, түрүүнд нь, өмнө
allow-зөвшөөрөх, өгөх, олгох, хүлээн зөвшөөрөх
amount-хэмжээ, зэрэг, дүн, тоо хэмжээ
approximately-бараг, ойролцоогоор
arrive-хүрэлцэн ирэх
assigns-томилох, тушаах, даалгавар өгөх
avoid-болиулах, хүчингүй болгох
beyond-алс, хол
blackness-харанхуй
codec-кодлол
commission-шимтгэл, хураамж
committee-хороо, комисс
common-ерөнхий, нийтийн, нийгмийн, жийрийн, хамтын
compose-эмхлэх, зохион бичих, зохиох,найруулах, эвлүүлэх
compressed-нягтруулагдсан, шахах
compression-нягтруулга, шахах
considerable-нилээд, ихээхэн
considerably-авч үзэх, анхаарч үзэх
contain-багтаах, тогтоох, дарах
content-агуулга, утга, багтаамж
contrast-ялгаа, ялгарал, эрс ялгаа
converting-хувиргалт
corner-өнцөг булан
critical-шүүмжлэлтэй, аюултай, бэрх
decoding-код тайлал
decrease-хорогдол, багасгал,цөөрөх
definition-тодохойлолт, үзүүлэлт
delay-хүлээлт, сааталт, хожимдол, хоцрох
demonstrate-үзүүлэх, заах, батлах
depend-хамгаалах, , найдах
describe-тайлбарлах, дүрслэх
detrimental-хохиролтой, хор хөнөөлтэй
difference-ялгаа, ялгавар, зөрөө
different-өөр, ондоо, ялгаатай
discuss-санаархах, завдах
distortion-гажуудал, гажилт
dot-цэг, цэгэн зураас, нарийн зураас
during-турш
each-бүр, бүхэн, тус тус
efficient-үр дүнтэй, ашигтай
eliminate-арилгах, хасах, үгүй хийх, устгах
eliminating-хасах, хаях
enhancement-нэмэгдүүлэгч, өсгөгч, сайжруулагч
ensure-батлах, хангах
entire-бүхэлдээ
envelope-дугтуй
equal-ижил, адил, тэнцүү
excessive-хэт их
existing-одоогийн байгаа байдал, оршин буй
facility-тоноглол, төхөөрөмж, багаж
feature-зүс царай, онцгой газар, гол чухам,өвөрмөц
field-талбар, талбай, хээр тал, салбар
flicker-анивчих, хэлбэлзэх, чичрэх
formerly-анхандаа, урьд өмнө
fuzzy-тодорхойгүй
generate-үүсгэн төрүүлэх, гаргах, үйлдвэрлэх
ghost-давталт, бүдэг дүрс
growth-өсөлт, өсвөр, хөгжил дэвшил
guard-хамгаалалт, хашилт, товлох
horizontal-хялбар, хэвтээ, хөндлөн
impairments-доройтол, сулрал
incompatible-үл нийцсэн, нийлэхгүй, таарахгүй
insert-оруулах, хавчуулах, хавсаргах
inspection-үзлэг, шалгалт, хяналт, ажиглалт
integrity-интеграл
intelligibility-сонсдоц, ялгац
interference-харилцан нөлөөлөл, шуугиан
interlaced-мөр алгасах
intervening-оролцох
lack-хүрэлцээгүй, байхгүй байх, гачигдах
linearity-шугамчлал
linear-шугаман
lossless-алдагдалгүй
memoire-тэмдэглэл, өөрийн түүх, эрдэм шинжилгээ, өгүүлэл
merely-зөвхөн, ердөө, болох
motion-хөдөлгөөн
New words
occupied-эзэнтэй, эзлэгдсэн
otherwise-өөрөөр, тохиолдол
overcomes-дийлэх, ялах, барих, дарах
persistence-шургуу зан, тэсвэр, тэвчээр
per-нэг бүрээс
portion-хэсэг, блок
practical-практикт хийж болох, үр ашигтай
previous-хуучин,
principal-үндсэн гол
propagation-ургуулах, үржүүлэх, дэлгэрүүлэх
proprietary-эзэмших
provides-бэлдэх, хангах
ptop
raster-ханалтын, торон
rate-хурд, хэр хэмжээ, давтамж
reasonably-үндэслэлтэйгээр, ухаалгаар
redundancy-илүүдэл
redundancy-илүүдэл, хувьсал, хуулбарлах
refresh-сэргээх, тэнхрүүлэх
regular-зөв, жинхэнэ, хэвийн, албан ёсны
rely-итгэх, найдах
requirement-шаардлага, хэрэгцээ, нөхцөл, болзол
require-хэрэглэх, орох, шаардах, тушаах
resolution-шийдэх, шийдвэрлэх
restored-сэлбэх, засах
result-үр дүн
retains-хадгалах, санах
return-эргэн ирэх, буцан ирэх
reveal-илрүүлэх, илчлэх
satisfactory-хангалттай, ханамжтай, шаардлага хангасан
scene-үйл явдал, шийдвэрлэх
show-гаргах, илэрхийлэх
slightly-бага зэрэг, үл ялиг,
squeezed-хавчих, шахах, хавчих
streams-урсах, цутгах,
sufficiently-хүрэлцэхүйц, хүрэлцээтэй
sufficient-хүрэлцэхүйц, хангалттай
syntax-өгүүлбэр зүй
tiny-өчүүхэн, өөдөсхөн, жижиг
trace-ор, мөр, тэмдэг, хаяг, мөр хөөх
transmit-дамжуулах, нэвтрүүлэх
transmit-дамжуулах, нэвтрүүлэх, явуулах
upper-дээд
variation-хувиралт, зөрөө, ондоо, өөрчлөлт
varies-янз янзын, зүйл бүрийн
varying-хувиргах, өөрчлөх
vertical-босоо шугам, эгц

new words

Bear-үүрэх, ачаалал даах
Resemblance-адил төстэй байдал
Delivered-хүргэгдсэн
Channel-суваг, хоолой, сувагжуулах
Household-айл өрх
Area-талбай, муж, бүс нутаг, орон зай
Receive-хүлээн авах
Least-хамгийн бага, өчүүхэн
Combination-хослуулал, нийцүүлэл
Entertainment-программ
Information-мэдээлэл
Bringing-авч ирэх, учруулах
Broad-өргөн, уудам, дэлгэр
Bandwidths-зурвасын өргөн
Into-дотор, дотогш,-руу
Threatening-заналхийлсэн, тулгарсан
Traditional-үндэсний
Method-арга барил, аргачлал
Providing-хангах, олгох, бэлдэх
Over-дээгүүр, дээр, илүүдэл
Rebuilt-дахин босгох
Way-зам
Broadband-өргөн зурвас
Application-хэрэглээ
Completed-төгссөн, дууссан
Earmarked-далд хийсэн
Available-хүчинтэй, чөлөөтэй, хэрэгтэй
Demand-шаардлага, хүсэлт, эрэлт
Market-зах зээл
Poised-тэнцвэртэй
Begin-эхлэх
Compete-өрсөлдөх, тэмцэлдэх
Provider- хангагч, нийлүүлэгч
Prepare-бэлтгэх, төхөөрөх
Faced-нүүртэй, царайтай
Competition-өрсөлдөөн
Own-өөрийн
Satellite-хиймэл дагуул, дахин дамжуулах станц
Better-илүү сайн
Quality-шинж чанар
Offer-санал барих, өргөх
Broadcast-өргөн нэвтрүүлэг
Converting-эргүүлэх, өөрчлөх, шинчлэх
Mandated-эрхийн бичиг
Transition-өөрчлөлт, шинчлэлт
Deadline-товолсон хугацаа, эцсийн хугацаа
Extended-урт, удаан, хугацаа сунгасан
Prevalent-давамгайлсан зорилго, өргөн дэлгэрсэн
Conference-хурал, цугларалт
Important-чухал, ач холбогдолтой
Facility-төхөөрөмж, хэрэгсэл
Soon-удахгүй
Routine-тогтсон дэг, хэв загвар
Customer-харилцагч, хэрэглэгч, захиалагч, үйлчлүүлэгч
Premise-угтвар нөхцөл
Switching-холболт, залгалт
Evolve-хөгжих, дэлгэрэх, өрнүүлэх, ялгаруулах
Influence-нөлөө, нөлөөлөл
Personal-хувийн, амины
Resent-саяхан, шинэ, өнөө үеийн, ойрын
Structure-бүтэц, зангилаа, байгууламж, барилга
Element-зангилаа, блок, эд анги, бүрдэл
Processor-боловсруулагч хэрэгсэл
Product-бүрэлдэхүүн, бүтээл, үр дүн, үйлдвэрлэх
Proprietary-эзэмшигч
Contrary-эсрэг, тэсрэг, урвуу
Principle-зарчим, үндэс, гол зүйл
Protocol-урьдчилсан гэрээ
Surrender-бууж өгөх, татгалзах
Impetus-өдөөлт, сэдэлт, урам, цочроолт түлхэц
Yield-гарц, бүтээмж, ургац, ашиг өгөх
Hardware-компютерийн техник хангамж
Interface-холбоо, зохицуулалт, хэрэглэгчтэй харилцах хэсэг
Same-адил, ижил, тэнцүү
Generation-үе, үүсэл, гаргалт, үүсгэлт
Run-зам, шугам, гүйцэтгэх, кабелийн дотоод сүлжээ
Platform-суурь, мөрийн хөтөлбөр, тайз, тавцан
Contain-агуулах, багтаах
Device-хэрэгсэл, байгууламж, багаж, бүрдэл хэсэг
Direct-шууд, шулуун, удирдах, чиглүүлэх, хандуулах
Contact-танилцах, харилцаа, холбоо, залгаас, хил зааг
Care-зовнил, анхаарал халамж, асрамж
Associated-холбогдсо, нэгдсэн
Excitement-сэтгэлийн хөөрөл, хөөр баяр
Industry-аж үйлдвэр
Suffer-зовох, тарчлах
Century-зуун, зуун жил, үе, нас
Revive-сэргээх
Organization-зохион байгуулалт, зохиомж, нэгдэл байгууллага
Severe-хатуу чанга, хахир ширүүн, хэцүү
Replace-сольж тавих, орлуулах, нөхөн сэргээх
Aging-хуучралт, элэгдэлт
Degree-зэрэг, дэс дараа, түвшин
Victim-золиос, хохирогч
Comprise-агуулах, багтаах
Equipment-тоног төхөөрөмж
Practically-үнэндээ, бараг
Wear out-хуучирсан, хугацаа хэтэрсэн
Motivation-шалтаг, сэдэлт, урамшуулал, өдөөлт
Gain-өсгөлт, ашиг, орлого
Feature-онцлог, чадвар, арга, шинж чанар, гол чухал
Based-суурилсан
Reach-хүрэх, дөхөх, дамжуулах, сунгах
Point-цэг, байр, оноо, асаагчийг хуваарилагчийн контакт
Manufacturer-үйлдвэрлэгч
Line-шугам, суваг, дараалал, зам
Situation-орон, байдал, байрлал, орчин
Differentiate-ялгах, салгах
Effective-тусгай, хүчинтэй, үр ашигтай
Raise-дээшлүүлэлт, ихсэлт, хураах, зээлэх
Both-хоёулаа, аль аль нь
Commodity-бараа, таваар
Exist-орших, байх, амьдрах
Possibility-боломж, завшаан
Exploit-ашиглах, эзэмших
Hilt-иш, бариул
Resolve-шийд, шийдвэр, зориг, зориглох
Mostly-ихэнхдээ, гол төлөв
Issue-асуудал, хэвлэл, дугаар тавих, олгох, хэрэг
Stable-тогтвортой, бат бөх, байнгын
Public-нийтийн, ил тод, ард олны
Ubiquity-юмнаас хоцордоггүй байх
Arise-үүсэх, бий болох, өнгөрөх
Consequent-үр дүн, уршиг, дараалсан, үр дагавар
Private-дотоод, зожиг, ганцаардмал, нууц
Weakness-дорой, муу газар, сул тал, дутагдал
Lie-худал хэлэх, заль, байршил
Strength-хүч тамир
Support-дэмжих, туслах
Decade-10 жил
Development-хөгжил дэвшил, өрнөл
Fail-эс чадах, осолдох, мартах, дутагдах
Occupy-суух, эзлэх, хөлслөх,эзэмших
Significant-олон талын ач холбогдолтой
Portion-хэсэг, хувь ноогдол
Discussion-яриа, зөвөлгөөн, маргаан
Station-зогсоол, өртөө, хэсэг, салбар, станц
Common-ерөнхий, нийтлэг
Type-төрөл
Voice-дуу хоолой
Regardless-хайхрамжгүй, үл тоомсорлосон
Whether-.....уу .....үгүй юу, эсэх
Separate-салгах, ангилах, хуваагдах
Latter-сүүлчээр, сүүлчийн
Getting-авах
Attention-анхаарал
Majority-олонхи, ихэнх, давамгайлсан
Automatic-өөрөө, автомат
Distribution-түгээлт, хуваалт, тархалт
Key-түлхүүр, товчлуур, код, тэмдэгт, үндсэн гол
Subject-өгүүлэгдэхүүн, сэдэв, шалтгаан
Facsimile-факсимил холбоо
Capacity-багтаамж, хүчин чадал, даац, эрх мэдэл
Inexpensive-хямдхан
Major-томоохон, чухал, голчлох
Fact-үнэн учир, баримт, чухамдаа, үйл явдал
Relocate-дахин байршуулах, шилжүүлэн суулгах
Jack-хөшүүрэг, залгуур, суурь, үүр
Interchange-солилцол, шилжилт, ээлж солигдох
Interchangeability-харилцан солилцох чадвар
Required-хэрэглэсэн
Across-хөндлөн
External-гаднах, өнгөн, гадаад
Gateway-шилжүүлэх гарц, дундын станц, сүлжээний гарц
Separate-салгах тусгаарлах, бие даасан, хуваагдах
Lip-уруул, амсар
Sync-синхрончлол
Apt-дөхөм, нийцтэй, -мтгий, -мхай
Multipoint-олон цэгийн, олон цэгт
Terrestrial-газрын, хуурай замын
Transmission-дамжуулалт, нэвтрүүлэг
Cost-зардал, үнэ,
Amount-хэмжээ, зэрэг, дүн
Justify-тэнцэтгэх, тэнцүүлэх, тэгшитгэх
Occasionally-хааяа, санамсаргүй, тохиолдлоор
Bridging-богино холболт, холбох
Dial-шатлал, дугаар цуглуулах, дуудлага хийх
Control-удирдлага, хянах, шалгалт
Unit-байгууламж, зангилаа, төхөөрөмж
Input-оролт, оролцоо
Location-байршил, нутаг,газар
Each-тус бүр, нэг бүр
Seize-эзлэх, барих, ойлгох, ухаарах
Allocate-байрлуулах, гаргаж өгөх, байршилыг тогтоох
Leader-удирдагч, ахлагч, тэргүүлэгч
Share-хуваах, хувьцаа, оролцоо
Current-гүйдэл, цахилгаан гүйдэлийн урсгал
Talk-яриа, хэлэлцээр, лекц
Discipline-дэг журам, ШУ-ны салбар
Approach-хандлага, арга, ойртолт
Evaluate-үнэлэх, тооцоолох, тогтоох, цэгнэх
Appliance-багаж, төхөөрөмж, цахилгаан хэрэгсэл
Set up-холболт тогтоох
Formal-албан ёсны, тогтсон
Level-түвшин, зэрэг
Compress-нягтруулагдсан, шахсан
Satisfactory-хангалттай, шаардлага хангасан
Per-нэг бүрээс
Lower-дор нам, буулгах, багасгах
Factor-нөлөөлөх, хүчин зүйл
Multiple-олон дахин, нийлмэл
Fundamental-үндсэн, гол,суурь
Fix-нэвтрүүлэх, тэмдэглэх, товлох
Portable-зөөврийн, авсаархан
Frequent-олон дахин давтагдах, дахин дахин ирэх
Relocation-шилжүүлэн байрлуулалт
Wideband-өргөн зурвас
Supply-цахилгаан тэжээл, хангамж, нөөц
Integration-интегралчлал
Assemble-цуглуулах, угсрах, хуралдах
Ensure-батлах, хангах
Compatibility-таарамж, нийцэл
Advisable-хэлүүштэй, зөвөлмөөр
Obtain-хүлээж авах, гаргаж авах, холбогдох
Vendor-борлуулагч, худалдаалагч
Integrate-нийлүүлэх, бүрэн болгох
Complete-төгс, дуусах, бүрэн хаах
Consider-авч үзэх,......гэж үзэх, бодолцох
Proprietary-эзэмшигч
Discuss-хэлэлцэх, зөвшилцөх
Encryption-нууцлалт, түлхүүртэй кодлуур
Particular-тодорхой, тусгай, нарийвчлал
Locality-суурьшил, байршил, бүс нутаг
Preclude-хаах, боломжгүй болгох
Holding-эзэмшилт, нөөц, хянах
Offset-шилжүүлэх, зөрөө, алдаа гарах шилжилт
Effective-тусгай, хүчтэй, үр нөлөөтэй
Option-сонгох, шилэх
Processing-боловсруулалт
Relationship-холбоо, харилцаа, ураг төрөл
Despise-муу үзэх, доромжлох, гадуурхах
Attendant-үйлчлэгч
Mainstream-зонхилох чиг хандлага
Product-бүтээгдэхүүн, үр дүн
Even-адил, төстэй, тэгш
Convenience-тохилог байдал, таарамж
Retrieving-буцаах, сэргээх
Away-цааш
Rail-бориул
Frustration-зогсоолт, тасалдуулга
Landing-газардалт, зогсолт
Hurry-яарах, сандрах
Reach-дамжуулах, хүрэх
Endure-тэсэх даах
Endless-дуусашгүй, тоо томшгүй
Prompts-яаралтай, түргэн
Enjoy-баясах, хэрэглэх, тааламжтай байх
Convenience-аятайхан, ашиг сонирхол, ая тух
Checking-саад, хяналт
Account-тооцоо, данс
Balance-тэнцвэр, дүүжин, үлдэгдэл
Stay-байх, үлдэх, буух, суух, хойшлуулах, бэхлэх
Yet-хараахан, бас, атал
Misused-буруугаар хэрэглэх
Properly-яг ёсоороо, сайтар
Applied-хавсарга
Great-их том, агуу, алдартай
Deal-хэсэг, тохиролцоо
Relieve-буцаах, сэргээх
Tag-хаяг, шошго
Accessible-нээлттэй, хандаж болох
Improper-зохисгүй, буруу, эвгүй
Generate-гарах, үүсэх
Frustrate-гацах, хавчих
Whatever-ямар ч, ямар нэг, юу ч, аль ч
Antipathy-дур гутах, зэвүүцэх
Feel-мэдрэх, бодох
Toward-чиг, зүг
Little-жижиг, бага, ялихгүй
Device-төлөвлөгөө, тоног төхөөрөмж
Way-арга, зам, зүг, ухаан
Apply-хэрэглэх, хавсаргах, ашиглах
Principle-зарчим, үндэс
Violate-харшлах, хүчирхийлэх
Practice-дадлага
Communicate-мэдээлэх, дамжуулах
Avoid-хүчингүй болгох
Regular-хэвийн, тогтмол
Update-сайжруулах
Personal-хувийн
Greeting-мэндлэл, мэндчилгээ, угтах
Convey-дамжуулах
Contrast-эсрэг, ялгаа
Either-дурын, нэг нь, аль нь ч, бас, мөн, эсвэл
Explains-тайлбарлах
Enhance-нэмэгдүүлэх, өсгөх
Accessibility-хялбар, дөхөм байх
Server-толгой машин, үйлчлэгч компьютер
Browser-дуудагч, ачаалагч, гаргагч
Enable-бололцоотой болгох, боломж олгох
Advertise-зарлах, тунхаглах
Presence-орших, холбох
Whether-..........уу үгүй юу эсэх
Beneficial-ач тустай
Avoid-зайлсхийх, зугтах,гажих
Disclose-илрүүлэх, илчлэх
Context-урьдах хойдох үгс, хам сэдэв
Include-хорих, агуулах, байх багтаах
Interactive-харилцан яриа
Response-гаралтын дохио тодорхойломж
Recording-бичлэг, бүртгэгч
Speech-яриа, хэлэх үг, илтгэл, аялгуу
Recognition-таних, танигдах, хүлээн зөвшөөрөх
List-хуудаслах, тоочих, гаргах, нэрлэх
Order-захиалах, зарлигдах, тайван байдал, дүрэм
Maturity-боловсрол, насанд хүрсэн, боловсорсон
Become-болсон, болох
Cousin-бүл, үеэл бөл ах, дүү, эгч
Route-зам, -аар явуулах, чиглэл
Select-ялгах, сонгох, сонголт
Carrier-зөөгч, дамнуурч
Step-алхам, мөр
Further-дараа нь,тэгээд, дэмжих
Converse-ярих, хөөрөх, эргүүлсэн урвуу
Pad-олбол, сунжруулах, зузаалах
Anyone-дурын, ямар ч, хэн нэгэн
Combination-хослуулах, хослох
Limit-хязгаар, зааг тууль
Allow-зөвшөөрөх, болох, өгөх, олгох
Command-тушаах, захирах, мэдэх
Instead-оронд
Keypad-нэмэлт, туслах гар
Immature-болоогүй, боловсроогүй
Steady-бат бөх, байнгын хэвшсэн,нэгэн жигд
Improve-сайжрах, боловсронгуй болох
Organization-зохион байгуулалт
Kind-төрөл, анги,чанар
Category-зүйл аймаг, зэрэглэл
Compress-шахах, дарах
Index-хэлхээс, жагсаалт гаргах
Stream-урсгал, горхи, цутгах, намирах
Session-хурал чуулган
Retrieve-буцаах, сэргээх
Verification-шалгалт, биелэл
Occasional-хааяа, тохиолдолын, ховор
Misapplication-буруу ашиглалт
Enormous-асар их, аварга, нүсэр аймаар
Potential-болмоор, чадамж, боломжтой
Delay-саатал, удаашрал, хожигдуулах

Chapter 22 -Abstract

The two fields are interlaced to form a frame. Acolor television signal has two parts: the luminance signal and the chrominance signal. A black and white picture has only the luminance signal, The chrominance signal modulates subcarriers that are transmitted with the video signal.
CATV system
Headend equipment generates local video signals and receives signals from a variety of sources including off-the-air broadcasts, communication satellites, or microwave relay or fiber-optic connections from other providers. The trunk cable is equipped with broadband amplifiers that are equalized to carry the entire bandwidth.
Hybrid Fiber Coax (HFC)
As cable technology improved, the bandwidth increased and more channels were added. As Internet traffic increases, the response time increases, generally in proportion to the number of subscribers.
The entertainment channels are applied to the distribution cable as always, but the Internet channels are combined to a lesser number of subscribers.

Videoconference
Videoconferencing has considerable appeal, primarily as a substitute for travel, but it has yet to become a mainstream application. With a stable private network in place, the quality is as good as ISDN. The Internet is not a suitable medium where true conference-quality video is required, so most external conferences will need an ISDN gateway.

chapter28

Voice-Processing Systems

Many people have a love–hate relationship with voice processing. Despised by many, voice mail and the auto attendant are mainstream products, even in the smallest of offices. We love the convenience of retrieving voice messages when we are away from the office but rail at the frustration of landing in voice mail when we are in a hurry to reach someone. We endure the endless prompts of badly designed automated attendants, but enjoy the convenience of checking our account balance 24 h a day. Voice-processing systems are here to stay; yet they are the most misused of telecommunications technologies. Properly designed and applied, voice-processing systems can save a great deal of time and relieve phone tag by making their users accessible while they are away from the phone, but improperly used systems generate phone tag and frustrate customers. Whatever antipathy people may feel toward voice processing has little to do with the devices, but with the way their designers and users apply them. The fundamental principle, frequently violated in practice, is to use voice technologies to make it easier for others to communicate with you, not as a way to avoid communication. Regular updates to personal greetings can convey information about how you can be reached in contrast to “I’m either on the phone or away from the desk,” which explains nothing. SIP proponents plan to enhance accessibility by using servers that can be updated with Web browsers to enable people to advertise their presence. It will be interesting to see whether SIP makes a beneficial change in those who use technology to avoid disclosing their presence. In the context in which we use it in this chapter, voice processing includes the following technologies:

_ voice mail,
_ automated attendant,
_ interactive voice response (IVR),
_ digital recording,
_ speech recognition.

These technologies are listed in order of their maturity. Voice mail has become such a mainstream application that few offices do not have it. Automated attendant, a close cousin of voice mail, enables callers to route themselves by selecting from a menu. IVR carries the process a step further by enabling callers to converse with a
computer by using the DTMF pad on their telephones. As anyone who has designed or used such a system knows, however, the triple-letter key combination of a DTMF pad is limiting. One answer is speech recognition, which allows the users to speak commands instead of using the telephone keypad. Speech recognition is immature, but it is steadily improving. Digital recording is required in many organizations that take orders of different kinds over the telephone. Products in this category compress, record, and index the voice stream, so a session can be retrieved for verification of what the parties said. Even given the occasional misapplication, voice-processing technologies have enormous potential for improving customer service and cutting costs. Voice mail makes it possible to leave messages across time zones, keeping voice inflections intact, and avoiding the misunderstandings that so often result from passing messages through a third party. IVR makes it possible for people to retrieve information outside normal working hours and without enduring the delays that often occur during peaks. The organization saves labor costs, employees are relieved of the mind-numbing task of repeatedly delivering the same information, and customers do not have to wait. The automated attendant enables callers to route their own calls quickly to the appropriate department without lengthy oral exchanges and enables the company to eliminate the cost of handling the call manually. Everyone benefits from voice processing if the applications are chosen carefully and administered intelligently. This chapter discusses the elements of the five principal voice-processing technologies and describes the features available. The applications sections discuss typical uses and precautions to observe in applying them. The chapter also covers digital announcers. Although these are not technically voice-processing devices, they have many of the same elements and are used behind PBXs and ACDs to deliver queue announcements to callers.

VOICE MAIL

Voice mail caught on slowly at first, but is now almost universally accepted and the market offers so many alternatives that it is practically a commodity. The feature packages are so similar that it is difficult for manufacturers to differentiate their products. The switch manufacturers generally do a better job of product integration than third-party developers, but as voice mail migrates from proprietary systems to servers, the proprietary aspects diminish. Voice mail has the potential for improving internal communications in most organizations. A high percentage of telephone calls are uncompleted because the called party is away from the desk or on the telephone, and the frustrating game of telephone tag begins. Properly used, voice mail enables people to communicate asynchronously by exchanging voice-mail messages. Calls can be exchanged across time zones, messages can be left and retrieved quickly when only a few minutes are available between meetings or flights, and the group broadcast feature enables a manager to convey information to everyone in the workgroup with a single call. A voice-mail system is a specialized computer application that compresses and stores messages and personal greetings on a hard disk that also holds the prompts. A processor controls the storing, retrieving, forwarding, and purging of files. Voice-mail systems connect directly to a PBX bus or through station ports. T1/E1 connections are common for large systems. Increasingly, the voice-mail application is migrating to servers, which may communicate with either a VoIP host or an IP-enabled computer by exchanging control messages across an IP network. Voice-mail service is available from service bureaus or behind a PBX or key system. The products and features are similar except for the scale and the method of identifying the called number. Service bureau systems are either stand-alone or integrated with a central office switch. Private voice-mail systems are integrated with the PBX or key system. Figure 28-1 shows a Nortel Call Pilot system that is integrated with an SL-100 PBX.

Voice-Mail Integration

PBX-integrated voice-mail systems provide features that enhance their value. To achieve integration, the PBX and voice-mail system must be designed to interoperate. A fully integrated voice-mail system offers several features that require direct communication between the voice mail and switching system:

_ Return to attendant. A caller, on reaching voice mail, can escape
to a message center or switchboard operator by dialing 0.
_ Multiple greetings. Voice-mail users may have different greetings for internal versus external calls or a different greeting when the phone is busy than when it is not answered. With time-of-day control the called party can vary call coverage and personal assistance options.
_ Called-party recognition. If the called party does not answer and the call forwards to an extension that is covered to voice mail, the original called-party’s greeting is heard.
_ Message-waiting indication. When a message arrives in a user’s mailbox the system activates a message-waiting light or applies stutter dial tone to remind users to retrieve messages.
_ Alphanumeric prompts. The voice-mail system may send alphanumeric prompts to display phones.
_ Security. The telephone system and voice mail may interact to prevent would-be hackers from dialing invalid extension numbers to place fraudulent calls.
_ Caller identification. The name of the person calling from within the system or the number of an external caller to the system equipped for caller ID is inserted into the message header.
_ Message forwarding. The user can forward a voice-mail message to another station with or without comment.

The first of these features allows the caller to escape from the voice-mail system and leave a message with a personal attendant, such as a departmental secretary. Lacking this feature, a caller can reach only the PBX attendant. The second feature, multiple greetings, conveys valuable information to the caller and allows the callee to treat callers more personally. If a caller hears a greeting that states the called party is on the telephone, the caller’s action may be much different than if he or she hears a message stating that the callee is out of the office. Furthermore, many companies prefer as a matter of policy that an attendant answers external calls, restricting automatic voice-mail answering to internal calls. The third feature, called-station recognition, is a major flaw of poorly integrated systems. With full integration, if calls cover to voice mail, callers always hear the greeting of the party they originally called, even if the call forwards to another station that is also forwarded to voice mail. With some systems, the caller hears the greeting of someone other than the callee, which is confusing. Message-waiting light illumination greatly affects voice mail’s utility to the station user. With an electronic telephone that displays the light on a feature button, the user may need to do nothing more than press the button to retrieve messages. Without the feature, the user must periodically call voice mail to check for waiting messages, which results in delays in returning calls. For users who are rarely in the office, message-waiting light illumination is of little or no value, but for users who are frequently in the office, it is an essential feature. Some systems substitute a short burst of stutter dial tone as an alternative, which is useful for off-premise stations or telephones that lack a message-waiting lamp. Alphanumeric prompts on display telephones are easier to use than the audible prompts that many systems provide. Users can press buttons to replay, forward, delete, or save messages. Security is a matter of great concern to all companies that have a voice mail. If the proper restrictions have not been installed, toll thieves transfer through voice mail to an outside line at the expense of the company. Integrated voice-mail systems exchange information with the PBX processor to prevent such transfers. Internal caller identification inserts the calling party’s name into the message header. The user can listen to headers and choose the most important ones to handle first.
Developers use three principal methods of achieving integration. The first is through a direct datalink from the voice-mail processor to the PBX processor. The PBX manufacturer may have a proprietary interface that it uses for its voice-mail product and may license it to others. Many PBXs also support SMDI, which exchanges messages with the voice-mail system indicating the callee’s identity, the calling number, and the message desk terminal to which the incoming call was delivered. A second alternative is through emulation of a display telephone. The PBX sends the calling number over the data channel from the switch to the telephone. The third method is integration through a CTI interface. The first method is faster and more efficient than the second, but it may be proprietary to the PBX manufacturer.
Third parties can reverse-engineer a display set to integrate voice mail with another system, but the method is slower than the datalink method. Furthermore, some features are available only through processor integration. CTI integration offers all the advantages of processor integration. Its main drawback is the expense of the PBX’s CTI interface. The extra cost may be considerable unless the interface is needed for other purposes. With this configuration, the voice-mail application resides in a server. The same server may also include IVR functions and connect to the PBX over a LAN.

Voice-Mail Features

The following is a list of the most important features in voice-mail systems in addition to those listed above as integration features.

_ Alerting. The message header is transmitted to a pager. The service is intended for use with short message service (SMS).
_ Audiotex. A “voice bulletin board” feature that permits the caller to choose from a menu of announcements.
_ Automatic purge. System automatically purges over-age messages to recover storage space.
_ Broadcast. User with this feature enabled in the class-of-service can send a group message to all box holders in the system.
_ Call recording. The user can press a button to record a conversation on voice mail. Ashort announcement informs users that the call is being recorded.
_ Class-of-service. Defines how a user may operate or interface with the system including such variables as the amount of storage allocated and the length of time messages can be stored before they are automatically deleted.
_ Disk usage report. System informs administrator of the percentage usage of the fixed disk storage unit.
_ Distribution lists. Permit users to establish lists of mailbox holders who receive messages when the appropriate code is dialed.
_ External device activation. The voice mail can be programmed to activate external relays, e.g., turning on the heat in the office.
_ Forms. Callers can be prompted to fill out a form such as registrant for an event in voice mail.
_ Future delivery. Allows you to postdate the delivery of a voice-mail message. Useful for sending reminders of things to do in the future.
_ Guest mailbox. Permits the system administrator to establish mailboxes for customers and temporary users.
_ Individual user profile. Permits individual users or classes of service to establish variables such as length of greeting, coverage for return to operator feature, and length of message retention.
_ Mailbox full warning. Informs the user when the mailbox is close to reaching capacity.
_ Message priority. Permits callers to designate a message as high priority. System reads out high-priority messages first.
_ Off-premise message notification. The system can be programmed to try a list of telephone numbers to deliver a voice-mail message. If the message is not delivered, it notifies the users of the attempts and the nondelivery of the message.
_ Out-calling. System can call subscribers at a predetermined telephone number, cellular telephone, or pager to notify them that they have received a message.
_ Undelete. Deleted voice-mail messages can be restored to the voice mailbox.
Unified Messaging

One deficiency with voice mail is the fact that messages are stored and retrieved in the same sequence in which they arrived. Some systems allow the user to listen to the headers and play the most important messages first, but the process is cumbersome
compared to e-mail in which the computer displays all messages. This makes it easy to skip through messages and save, delete, and forward them in any sequence. Unified messaging brings these benefits, which are inherent to e-mail, voice mail, and fax. Aunified-messaging client runs on the desktop computer and
links to the voice-mail server over the office network. It enables the user to handle voice mail, e-mail, and fax messages on the computer screen with no regard to the device that created them or will retrieve them. Using keyboard and mouse the user can replay, save, delete, forward, and otherwise handle and dispose off all
types of messages. Manufacturers have been touting this technology for several years, but it has not quite caught on. The main problem has been return on investment. Unifiedmessaging products are purchased with hard dollars and, for the most part, are justified with soft dollars. Managers find it difficult to demonstrate that unified messaging improves productivity for most workers. For workers who stay at their desks most of the day, voice mail without unified messaging is quite adequate. The commands for replaying, saving, deleting, responding to, and forwarding messages may not be intuitive, but once they are learned, the benefits of handling them on a PC screen instead of the telephone are, at best, marginal. Traveling and mobile people, on the other hand, can make good use of unified messaging. Voice messages and faxes can be attached to e-mail and retrieved from a laptop computer. Avoice synthesizer can read out file attachments, including fax-to-text conversion, if necessary. Eventually, speech-to-text technology will reach a point that voice mail can be converted to e-mail, but for now it is easy enough to forward voice mails across a network as a file attachment. Speech recognition also plays a part in unified messaging by enabling users to speak commands instead of using the telephone keypad. This relieves users of the need to remember which keys to press, but it may not work perfectly from a cell phone in a marginal coverage area or over a compressed VoIP circuit. Eventually, unified messaging will become a standard feature of voice mail.
The main inhibitor today is its cost. It is a proprietary application and, although it is mostly software, it has not reached the point that mass production has brought the cost within easy reach.

Networked Voice Mail

Alarge multisite operation can often bring its employees closer together with networked voice mail. If PBXs are of the same manufacture and are networked together, one PBX can host the voice mail and others can share it. Shared voice mail requires networking software in the PBXs. If the products are of different manufacture and if both are compatible with QSIG, this may offer a viable alternative for shared voice mail. Asecond method is networking the voice-mail systems themselves as shown in Figure 28-2. This method is effective when each site has many users. Messages are stored on the local voice-mail system, which reduces the network traffic compared to a shared voice-mail system. Networked voice mail permits users to have a mailbox in a distant PBX and have the messages delivered to their own voice mailboxes. For example, a sales manager could provide local telephone numbers for key clients in several different cities. Managers with staffs in more than one location can maintain distribution lists and forward calls across the network.
Networked voice-mail systems use point-to-point lines, an IP or frame relay network, or dial-up to transport messages between locations. Messages can also travel across the Internet. Since the message is being sent as a file, the delay inherent in the Internet is not an important issue, but packet loss will degrade usability. Systems from different manufacturers can be linked through a standard known as audio message interchange service (AMIS). AMIS standards exist for both analog and digital interchanges. The latter is the most effective because the digitized messages can be forwarded across the network without being converted to analog from the disk and then converted back to digital again for storage at the user’s location. Note that the AMIS interface must be provided separately for each pair of PBXs, so universal networking requires both products to support the standard.


Stand-Alone Voice Mail

In a stand-alone configuration, users dial into the voice mail over the PSTN. Many service bureaus and almost all LECs and cellular providers offer voice mail to outside callers. Service bureau voice-mail systems normally have large capacity— often sized in tens of thousands of mailboxes. If the voice mail is integrated with the central office switch it can cover a busy or unanswered line. Many service bureaus do not associate the voice mailbox with a specific telephone line. The user is given a telephone number that connects the caller into the box directly. In this respect it is little different than an answering machine. Service bureau voice-mail systems are effective for users who need a few mailboxes and cannot justify the purchase of a private system. They are also effective for users who are out of the office a great deal and have no need for message-waiting lights to indicate call arrival. The lack of message-waiting lights is one of the chief drawbacks of stand-alone systems for people who are regularly in the office, but
most systems can send a message to a pager or send an e-mail to signal the arrival of a message. Asecond drawback compared to integrated voice mail is the dead-end nature of the medium. When a call enters the mailbox, the caller’s only options are to leave a message, hang up, or possibly send a message to a pager.
The earliest service bureaus were exclusive to voice mail, but many now offer unified-messaging features such as reading e-mail over the telephone with text-to-speech and forwarding voice-mail messages to an e-mail address as a file attachment.

AUTOMATED ATTENDANT

The automated attendant is the most misused and maligned of the voice-processing technologies. The system answers the telephone and offers the caller a menu of choices such as “dial 1 for sales, 2 for service, 3 for engineering,” and so on. A properly designed system can save time for callers, but systems with lengthy
prompts and endless menus frustrate callers. The automated attendant is usually a feature of a voice-mail system, but the two are separable. IVRs can also be programmed to support automated attendant functions. Many companies prefer not to have their customer calls answered by an automated attendant. Different numbers or separate trunk groups can be configured
so that the automated attendant answers employee calls, while those to the main number go to the operator. In most systems, pressing 0 returns the caller to the attendant. Most systems allow callers to bypass the prompts and route directly through to the desired function, which works well if the caller knows the prompts.
Automated attendant can substitute for DID. The system prompts the caller to enter the extension number if known, dial by name, or wait for an operator. This is an effective tool if the caller knows the extension number or the name of the person they are calling. If not, an operator must be available to transfer the call. Name dialing is available on most automated attendants and IVRs. The
caller dials enough digits of the last name to satisfy any ambiguity. The system responds with the called-party’s name, often in the person’s own voice. Large companies are likely to have several people with the same last name. The system may prompt for the first name or offer a menu of choices. The second use of automated attendant is to enable callers to route their own
calls to an answering position by dialing a code from a menu of choices. The system manager must take care in creating the menu, because it is here that callers experience frustration. If too many choices at a menu level or too many menu levels
are offered, callers will be unable to remember them and have to start over or return to the attendant. A good policy is to permit no more than four or five choices at each menu level and no more than two or three menu levels. The system should be set up to allow callers who know the menu to dial the code immediately
without waiting for the prompt.

INTERACTIVE VOICE RESPONSE

IVR prompts callers to enter information such as an account number via DTMF dial and passes it to a server. The server processes the request and passes it back to the IVR, which reads the information to the caller. Banks and credit unions use
IVR to enable customers to obtain their account balances without waiting for an agent. In addition to financial institutions, IVR can support many applications where telephone service representatives receive simple requests from callers, key them into a terminal, and read the results from the screen. Examples are informing customers of backorders and prompting them to confirm or cancel their order, registering people for events, and delivering information such as status of a pending public assistance request. Properly designed, the application can save time for both caller and the company. A typical session involves customer identification by account number and password as the first step, after which the IVR presents a menu of choices. Within a range of choices callers can send instructions to the computer or query the database. The IVR responds with audio announcements, confirming the transaction or delivering the information to the caller. One of the earliest applications was LECs’ directory assistance. After receiving a request from the customer and looking up the number, the operator transfers the call to an announcement unit, which completes the transaction. LECs’ intercept services are another example. When the caller reaches an intercepted number the system responds by announcing that the old number is disconnected and is reading the new. IVR voice announcement technology falls into two categories. The most versatile method is voice synthesis, in which the characters coming from the computer are formed into words by a device that emulates the human larynx. The second form is a series of words stored in the memory or on the disk, which are triggered into the voice stream as needed. The synthesizer method is understandable, but the voice may sound accented. The stored voice method sounds natural, but the vocabulary is limited to what is stored, whereas a voice synthesizer can pronounce nearly every word. IVR should be considered as more than just a voice-response unit. If Web access is available, that is usually a more effective way to deliver information, but for callers without Web access, an IVR is an alternative. Here are examples of IVR
applications:

_ Automated order entry and status inquiry. Callers can access databases to place an order from a catalog, check availability and price, and check the status of pending orders.
_ Status verification. Callers can verify various types of information such as credit cards, employment, insurance, and other such information that can be delivered after authenticating the caller. Frequent fliers, e.g., can enter their account number to determine their current award status.
_ Time reporting and employee information. Field personnel can report time to a system that tracks attendance, provides information on accumulated leave, and other such employee information.
_ Dealer locator service. The IVR can prompt callers to enter their ZIP code for the name of the nearest dealer.
_ Fax-on-demand. The voice-response unit can lead callers through a menu of document choices. When the document is selected, the system prompts for a fax number and sends the fax immediately.
_ Student registration. Colleges and universities use IVR to enable students to register for classes from a DTMF telephone. Callers can use IVR to register for seminars and other events.
_ Appointment rescheduling. Clinic patients can reschedule their own appointments by calling into an IVR and identifying themselves by patient number. Clinics can also use the outdialing capability to remind patients of appointments.
_ Frequently asked questions. Support organizations can forward callers to an IVR to listen to the answer to questions. For example, a bar association lists attorney specialties and a hospital can offer self-help information to callers.
IVRs can be stand-alone or they can connect to a PBX over analog or digital ports. For more versatility they can connect through a CTI port. The CTI connection is important when callers transfer from the IVR into a call center to complete additional transactions. The IVR should forward enough information that the
agent does not need to ask the caller for his or her account number because it is already known. In addition, if the agent sees the nature of the caller’s activity in the IVR, it offers clues about the reason for the call. With an integrated IVR, callers can even be routed in ways that they least expect. For example, a caller with a delinquent account might be routed to the collections department when the account is accessed through the IVR.

DIGITAL RECORDING

Many companies must record calls as a way of confirming later what the parties said during the session. Stockbrokers, hospitals that offer advice over the telephone, catalog companies, and other such organizations sometimes need to retrieve the details of a call to resolve disputes. Digital recorders provide an array of voice channels that are digitized, compressed, and stored on a disk. Usually, the disk has removable media for archiving the calls. The products also time stamp the calls and provide output devices that can be used to retrieve the call. The system may provide for time synchronization from an external source such as GPS or radio station WWV. Recorders are available to connect to either analog or digital lines and to trunks of all types. They may monitor extensions or trunks in real time through a passive tap. Calls can be retrieved based on variables such as channel, start time,
call length, dialed number, caller ID, or ANI. Some products convert recordings to .wav files for e-mailing, burning to CD, or playing on an audio player. Products also typically report statistics on numbers and durations of calls.

SPEECH RECOGNITION

The dream of a product that does near-perfect speech recognition has existed for a long time and eventually the product will arrive. Speech recognition has improved steadily as a result of better algorithms and faster computers, but it is not quite there yet. Dialects, accents, vocabulary, and inflection all complicate the
problem of teaching a computer to recognize voices. Then there are homonyms such as two, too, and to, which can be distinguished only through context. Speech recognition takes computer power and plenty of it, but the potential rewards are
enormous. Telephony has many applications for speech recognition. The telephone instrument suffers from its keypad limitations. Dozens of products are available today to work around the shortcomings, but they have difficulties of their own. The PDA with a screen-operated stylus keyboard is one approach, but it is slow and awkward. Miniaturized keyboards are plentiful, but hardly suitable for anything but clumsy typing. The real answer will come through speech recognition. At today’s state of development a computer can be trained to recognize a wide vocabulary from a single speaker with a reasonable degree of accuracy. Equipment can understand simple spoken commands from a broader range of callers and can recognize numbers and some simple words. This often makes it possible to replace an automated attendant. For example, a dialog could read “for sales press or say 1, for customer service press or say 2,” and so on. This method can solve the problem of directing calls for users who do not have DTMF telephones. High-end products can do an even better job of recognizing words spoken by random speakers with a high degree of accuracy. Managers should watch speech recognition closely and be prepared to adopt it when it can help them reduce costs or improve customer service. Speech recognition does a reasonable job of replacing the DTMF pad for making selections from a menu where the range of responses is narrow. In a library, e.g., the system could ask the caller to speak the department he or she wants. If the caller says “science” the system could prompt “do you want social science or physical science?” The answer is in a predictable range, allowing the system to carry on a dialog until it is clear where the call should go or until an attendant intervenes. When it comes to communication with the telephoning public, the computer’s vocabulary narrows considerably. Computers can recognize numbers with a reasonable degree of accuracy regardless of dialect, and it is easy to read them back for confirmation. Speech recognition can support directory access by asking callers to say the last name of the person they want to speak to and then reading back possible alternatives. The result is fallible, but the application is improving and will get better.
The primary uses for speech recognition today are account number recognition and call routing. As the technology improves, the applications will replace some of the mind-numbing tasks of today. Directory assistance is high on the list. Customer service centers can greatly multiply their effectiveness by doing a better
job of screening and routing calls. For example, a speech recognition system could ask several questions that enable it to route calls to an expert. By contrast, today’s expert agent applications in an ACD have limited screening capability.
Verizon uses speech recognition to handle customer repair requests. The application is impressively natural sounding and undoubtedly saves the company money, but callers find it much less effective and more time consuming than talking to a human.
Speech recognition has already had some positive impact on telephony, but compared to its potential, the surface has merely been scratched.

DIGITAL ANNOUNCERS

Digital announcers provide information announcements in call centers, announcements-on-hold, intercepted number announcements, and a variety of such tasks. Most large PBXs need to route callers to announcements—frequently if they support call centers. Voice mail can provide occasional or infrequent
announcements, but digital announcers permit multiple callers to listen to the same announcement simultaneously, which many voice-mail systems do not support. PBX manufacturers offer digital announcers as cards that plug into universal slots. Systems are also available as stand-alone units that connect to trunk or
analog station ports.

VOICE-PROCESSING APPLICATION ISSUES

Users sometimes perceive voice mail as just a convenient answering machine, which has a tendency to limit its usefulness. Aproperly chosen and applied system can improve the effectiveness of the company’s staff by making them more accessible to customers and other employees. Voice mail has become so effective that it is indispensable to most organizations. Its applications are too numerous to list and, in most cases, are self-evident. Some creative uses that are not so obvious are:
_ A hospital offers voice mail for its patient rooms, allowing patients to receive messages while they are asleep, in surgery, etc., and play them back at their leisure.
_ A public telephone service provider allows a caller who reaches an unanswered or busy telephone the option of leaving a voice-mail message for later delivery. This is a valuable service for callers who cannot afford to wait.
_ A hospital posts its job openings in voice mail, segregated by licensed, nonlicensed, and office occupations. Callers can listen to descriptions of the jobs available and route themselves to the employment department to get more information.
_ A district school provides its teachers with a nonintegrated voice mailbox so that parents can leave messages for callback without interrupting either staff or teachers during class hours. The system forwards the messages as .wav file attachments across the data network.
_ A food processing plant provides guest mailboxes for its growers to inform them of recommended planting schedules and the availability of seeds and fertilizers. During the harvest season, daily tonnage quotas are left in voice mail. Not only does this system eliminate calls to farmers who are away from the telephone, but also makes it possible for the processing plant to verify that the message has been retrieved. To gain maximum benefit from voice mail, an organization must ensure that
its employees do not abuse the service. The most frequent abuse is the tendency of some users to hide behind voice mail, using it to answer all calls, which they can return at their convenience. When used this way, voice mail aggravates, instead of alleviating the problem of telephone tag. Improperly designed and applied voice mail and automated attendant systems have led to the creation of the term “voice-mail jail,” which refers to the situation in which a caller is locked in the system and cannot escape to get personalized assistance. A well-designed system should be brief and clear in its instructions and should give callers a choice.
Many companies are reluctant to use voice mail with their customers because of the impersonality of the service. The first contact a company has with a new customer usually should not be through voice mail, but when the relationship is firmly cemented, voice mail can be as advantageous to a customer as it is to
employees. The key is to leave the caller in control. Many companies answer outside calls with an attendant, but offer the caller the option of being transferred to the user’s voice mail. Even if messages are taken manually, the receptionist can read
them into voice mail or send them by e-mail, which is usually a more effective means of distributing messages than writing them on message slips.

Evaluating Voice Mail

Evaluations of voice mail, automated attendant, and audiotex systems should be based on features and on the criteria listed below, which discusses the most important features.

Port and Storage Capacity

Voice-mail systems are sized by the number of ports and hours of storage. The number of ports limits the number of callers that can be connected simultaneously. Ports are required for both leaving and retrieving messages and are occupied while callers listen to prompts or users update their personal greetings. The number of ports required can be calculated from the number of accesses and the holding time per access during the busy hour. (See The Irwin Handbook of Telecommunications Management for an explanation of how to calculate voice-mail port and storage requirements.) Designing the system with the correct number of ports is important. Having too many ports increases the cost of the voice-mail system. Having too few restricts the ability of callers to reach voice mail and blocks users when they attempt to retrieve messages. Ports normally are added in increments of two to four depending on the manufacturer. Large voice-mail systems may connect to the PBX over T1/E1 ports. The type of integration often affects the efficiency with which the voice-mail system uses ports. A popular feature on many systems is outcalling, which is the ability of the voice-mail system to dial the user’s pager or cellular phone. This feature requires ports to handle both incoming and outgoing calls. A tightly integrated system can assign any port to either type of call, but some systems may require separate incoming and outgoing groups of ports, which increases the total ports needed.
Voice-mail systems that are associated with traditional PBXs use physical ports for the connection. Each time a message crosses a port, it is converted between voice and whatever compression algorithm is used. Too many compressions and decompressions can affect intelligibility. For example, when a caller leaves a voice-mail message it is digitized, compressed, and stored. When the user retrieves it, it is decompressed and converted to analog. If it is forwarded to another user across a network and covers to voice mail on the distant system, it is digitized again. If the network is IP, it may be converted to a different compression algorithm. It is important to understand exactly how the manufacturer and vendor set up the system to avoid quality degradation. The amount of storage required is highly variable and depends on the number of users and the number of stored messages per user. It also depends on whether disk capacity varies with the announcement messages and how efficiently the manufacturer packs the disk. Efficient packing algorithms compress the silent intervals so that the disk space is not wasted. As a rule of thumb in sizing voicemail systems, the average user takes about 3 to 5 min of storage for greetings and messages. Asystem serving 100 users, therefore, would require 5 to 9 h of storage. Heavy users or those who are not careful to purge their old messages may require more than 5 min of storage on the average. The voice-mail system’s purging algorithm also affects storage efficiency. The more effective systems inform the administrator when the disk is reaching capacity. Over-age messages are manually or automatically purged after a specified time. In addition, most systems provide for different classes of service and can vary the amount of storage a user can have before callers receive a full-box message. Hard disks are so inexpensive that message storage may be of little or no concern. Some manufacturers charge for storage and, even though the hard disk has plenty of capacity, the owner must pay to have it unlocked.

Integration with a PBX

The most important consideration in evaluating and using a voice-mail system is the degree to which it integrates with the PBX. This is not to say that integration is always necessary; often the application needs a stand-alone voice-mail system. For
most office workers, however, an integrated system provides essential features.

Compression Algorithm

All digital voice-mail systems use some form of compressed voice technology to digitize and store messages and announcements. Part of the compression is gained by pause compression and expansion, in which the duration of a pause is coded instead of the pause itself. Voice-mail systems use pause compression to
speed or retard playback. If a listener wants a faster playback, the system shortens pauses; for a slower playback, it lengthens them. In addition, the specific technology used for digitizing the voice affects the efficiency of the system. The more the voice is compressed, the less natural it sounds and the less storage space it occupies. The best way to evaluate this feature is to listen to the voice quality of several different systems and compare voice quality. Pay particular attention to conditions that might result in excessive analog-to-digital conversions.

Port Utilization

The number of ports determines how many users can leave and retrieve messages simultaneously. Not all ports are necessarily available for full voice-mail use. Some systems require dedicated ports for automated attendant. Some systems require separate ports for outgoing messages such as calls that the voice-mail
system places to a paging or cellular radio system.

System Reports

System reports can be used to determine how efficiently the system is being utilized. Reports should provide information such as the following:

_ number of messages sent and received by a user;
_ average length of messages by user or group;
_ percentage of disk space used;
_ busy-hour traffic for various ports;
_ number of times all ports are busy;
_ message aging by individual mailbox;
_ number of messages not deleted after specified time.

Networking Capability

The cost of voice mail can be reduced by networking multiple voice-mail systems to act as an integrated unit. From the system administrator’s standpoint, an important issue is how to maintain distribution lists across the network. Some systems exchange messages that automatically update the other systems on the network. Another important function of networked voice mail is how systems exchange messages. In some systems, the voice-mail system can transmit messages as IP packets.

Security

The voice-mail system must prevent callers from dialing invalid extension numbers and thereby connecting through to trunks. The system administrator should be able to force password changes and to require nontrivial passwords of a minimum length.

Evaluating Unified Messaging

An important issue in unified messaging is how and where the messages are stored. This is not uniform among products. Voice mail, e-mail, and fax usually arrive on different servers, although many voice-mail products also support fax reception. An important issue in evaluating products is whether the message remains stored on the server it arrived on or whether it is transferred or copied to a different server under certain conditions. Some products combine e-mail and voice mail into a single server that also retains any faxes that arrive via voice mail. If faxes arrive on a separate server, which is often a third-party product, integration
with unified messaging will probably require custom software development. Another issue to consider is how unified messaging is priced. Regular voice mail carries a cost for the platform plus the hours of storage and number of ports. Some vendors also charge a fee per user, but many do not. Unified-messaging pricing is usually based on the number of users. This enables the customer to start with a few users to determine if the product pays off and expand it if it does. In addition to the per-seat license, the customer must provide a server. The administrator’s main issue is how to control storage. Many users are not diligent about
deleting messages and the storage capacity can be exceeded unless the system has some kind of automatic purge.

Evaluating Automated Attendant

In applying an automated attendant design, administrators should consider its effect on callers. Frequent callers usually have no problem navigating the menus, but a first-time caller may be baffled by the variety of choices. Any company considering an automated attendant will be well advised to study the application
carefully, design it intelligently, test it thoroughly, and listen to the comments of callers. Automated attendant substitutes for DID, particularly outside business hours. It reduces labor for console attendants and, in many cases, it is advantageous to the customer. Agood menu is a fast way of reaching the right destination in a call center. Employees and frequent callers can be told that when the company’s main number is answered they can immediately dial an extension number, which is faster than talking to an attendant.

Evaluating Audiotex

The audiotex feature of voice mail is a useful means of distributing information. Callers receive a menu of choices. They can select two or three levels of menu before reaching the desired information. For example, a university might disseminate class information via audiotex by listing the major courses of study—
science, liberal arts, engineering—on the first menu, the field of study—biology, botany, chemistry—on the second menu level, and class—freshman, sophomore— on a third. If the menu choices are no more than the caller can easily remember, this can be an effective way of delivering information. The system should be designed to enable callers to interrupt the menu by pressing a special key such as “#” to repeat. The most important criteria in evaluating audiotex are the types of host interfaces, application development tools, and local databases supported.

Evaluating IVR

Many of the same criteria as voice mail can be used to evaluate IVR. A major exception is the fact that the interface between the host computer and the IVR must be programmed. Shrink-wrapped software is available for some applications, but most are custom programmed—often by a system integrator that provides the IVR hardware and the company’s software application. Voice quality, ease of programming, and quality of vendor support are important considerations in IVR. Many systems provide application development tools that provide a high-level language the developer can use. In addition, the following criteria should be considered with IVR:

_ Hardware platform. Determine how many ports are available, what the maximum capacity is, and how much it costs to expand. What kind of platform does the system run on? What operating system does it use?
_ Software. Check the features that the system supports. Does the
manufacturer have a good record of introducing new features to keep pace with competition? What is the cost of new software releases? Has the application been programmed by a third party who makes it available for a fee or is it necessary to train or hire an application developer? If the latter, how much does the development kit cost and how easy is it to learn? What kind of debugging tools are available?
_ Integration. Determine how the system interfaces to the PBX or telephone system. Is it a proprietary interface that integrates with the PBX’s processor or is it a standard analog telephone interface? The former is more versatile, but the latter can be transported to other applications more easily and may integrate with any PBX. Determine how easily a caller can transfer to a live attendant. The system ideally should not require callers to re-identify themselves when transferring from IVR to an attendant.
_ Speech generation method. Does the system synthesize speech or use stored speech fragments? How natural does the speech sound? Can words or phrases unique to your operation be added easily?
_ Growth capability. How many ports does the system support? Does it have the processor power to handle as many simultaneous callers as there are ports? Are you given the tools to measure and verify performance?
_ Reporting capability. Does the system provide usage statistics? What form are they in? Can they easily be translated into service-related reports? Can the statistics be extracted while the system is active?

Evaluating Speech Recognition Equipment

The primary concern with speech recognition is its accuracy, which can be tested by observing the result with a variety of callers. Any system purchased today will undoubtedly be improved in the future, so determine the developer’s commitment to continued research and development and find out how the updates are
introduced and at what cost. Pay particular attention to the application. The best results will be achieved with simple applications that require recognizing a limited number of short words such as numbers, alphabet, department names, etc.

Evaluating Digital Recorders

The primary factors in evaluating a digital voice recorder are:
_ Security. Can voice sessions be kept secure from unauthorized access while still making them available to supervisors who need to review the session? Are recordings tamper-proof so they can be admitted to court sessions if necessary?
_ Accessibility. How easy is it to find the session from the client
workstation?
_ Clarity. Is the voice compression algorithm good enough that voice can be retrieved with a high degree of intelligibility?
_ Archiving. How easy is it to archive the recordings onto long-term
storage media such as digital audiotape or DVD?
_ Maintainability. Is system adequately alarmed? Does the system provide disk mirroring or other methods of fault tolerance? Is it secure against data loss during full disk conditions?

Evaluating Digital Announcers

Digital announcers are available as stand-alone devices that can interface to any PBX or public access line and as integrated devices that fit into a card slot in a PBX. It is important to evaluate the application carefully before buying an announcement system. The primary criteria in evaluating digital announcement systems are:
_ Storage capacity.
_ Number of ports.
_ Voice quality.
_ Method of integration with the PBX—through the bus or through a port.
_ Method of storing the announcement. Is it on volatile memory? How is it protected against power outage?
_ Method of updating the announcement—locally, remotely, or through a professional service. As with voice mail, the primary criteria in selecting a system are the amount of message storage and the number of channels required. It is also important to decide how the message will be changed. A permanent message such as an informational message about a company’s product line probably would be recorded professionally and rarely changed. The message might even be encoded on a chip before it leaves the factory. Conversely, a school providing announcements about
closures due to weather will want to record messages locally and, perhaps, from a remote location.
The control circuitry should determine when to connect the caller to the announcement. Some messages play only from the beginning; in other cases the listener can barge in on the message wherever it happens to be in a cycle. For example, if a promotional or informational message is being played, it would be appropriate to break in at only certain spots and the message would play only
once. Messages on hold might play repeatedly while the caller is on hold or the system might vary the message depending on how long the caller waits. Voice quality is another important consideration. As with voice mail, the higher the degree of compression, the lower the storage cost and sometimes the lower the voice quality. The best way to evaluate quality is to listen to a sample.

chapter-22

Video Systems

Today’s video systems bear little resemblance to cable television (CATV) systems of yore. Those delivered a dozen or so channels to households in areas that could not receive signals off the air. Today, cable systems deliver at least 70 channels with a combination of entertainment and information services, bringing
broad bandwidths into homes and businesses and threatening to upset the traditional method of providing telephone service. Over the past few years, cable companies have rebuilt their networks into two-way broadband systems. The Internet was the first application, but once that was completed, some of the bandwidth
earmarked for IP was available for video-on-demand. Cable has captured more than half the broadband access market in the United States, and now it is poised to begin competing with the LECs to deliver telephone service. As the cable providers prepare to compete with the telephone companies, they are faced with competition of their own from satellite providers. Satellite video is digital and delivers better signal quality than the analog channels that the cable providers offer. Most cable providers also offer digital channels, and the broadcasters are converting their analog signals to digital. The FCC has mandated a transition to digital by the end of 2006 for broadcasters that use the airways, but that deadline will probably be extended. While entertainment is the prevalent use of video today, videoconferencing is an important facility for businesses and desktop video will soon be routine.
Distance learning for schools and telemedicine for healthcare organizations are emerging applications. As with most technologies, the key to expansion has been the development of standards. For years, the videoconferencing manufacturers
produced equipment with proprietary standards, which meant they could not interoperate. Then ITU-T completed its work on H.320 standards, which enables equipment to interoperate over dial-up or dedicated digital facilities. For packet networks, H.323 standards enable video communication across IP and frame relay.
AT&T demonstrated its Picturephone at the 1964 New York World’s Fair, but it turned out not to be practical. Like many other product developments, however, it was merely ahead of its time. Conferencing equipment built into desktop computers is becoming a regular feature in most companies and many homes. With
the growth of broadband connections to most homes and businesses, video will become a common enhancement for telephone calls.

VIDEO TECHNOLOGY

Video signals in North America are generated under the National Television Systems Committee (NTSC) system. In Europe they are generated under two different and incompatible standards: PAL (phase alternate line) and SECAM (sequential couleur avec memoire). An analog video signal is formed by scanning an image with a video camera. As the camera scans the image, it creates a signal that varies in voltage with variations in the degree of blackness of the image. In the NTSC system, the television raster has 525 horizontal scans, forming a raster that is composed of two fields of 262.5 lines each. The two fields are interlaced to form a frame (Figure 22-1). The frame repeats 30 times per second; the persistence of the human eye eliminates flicker. Since the two fields are interlaced, the screen is refreshed 60 times per second. On close inspection, a video screen is revealed to be a matrix of tiny dots. Each dot is called a picture element, abbreviated pixel. The resolution of a television picture is a function of the number of scan lines and pixels per frame, both of which affect the amount of bandwidth required to transmit a television signal. The NTSC system requires 4.2 MHz of bandwidth for satisfactory resolution. Because of the modulation system used and the need for guard bands between channels, the FCC assigns 6 MHz of bandwidth to analog television channels.
The signal resulting from each scan line varies between a black and a white voltage level (Figure 22-2a). A horizontal synchronizing pulse is inserted at the beginning of each line. Vertical pulses synchronize the frames as Figure 22-2b
shows. Between frames the signal is blanked during a vertical synchronizing interval to allow the scanning trace to return to the upper left corner of the screen. Acolor television signal has two parts: the luminance signal and the chrominance signal. A black and white picture has only the luminance signal, which controls
the brightness of the screen in step with the sweep of the horizontal trace. The chrominance signal modulates subcarriers that are transmitted with the video signal. The color demodulator in the receiver is synchronized by a color burst consisting of eight cycles of a 3.58 MHz signal that is applied to the horizontal
synchronizing pulse (Figure 22-2a). When no picture is being transmitted, the scanning voltage rests at the black level, and the television receiver’s screen is black. Because the signal is amplitude-modulated analog, any noise pulses that are higher in level than the black signal level appear on the screen as snow. A high-quality transmission medium keeps the signal above the noise to preserve satisfactory picture quality. The degree of resolution in a television picture depends on bandwidth. Signals sent through a narrow bandwidth are fuzzy with washed-out color. The channel also must be sufficiently linear. Lack of linearity results in high-level signals being amplified at a different rate than low-level signals, which affects picture contrast. Another critical requirement of the transmission medium is its envelope delay characteristic. Envelope delay is the difference in propagation speed of the various frequencies in the video passband. If envelope delay is excessive, the chrominance signal arrives at the receiver out of phase with the luminance signal, and color distortion results.

Digital Television

As with telephone transmission, analog impairments can be avoided by converting the signal to digital. An uncompressed studio-quality signal is about 270 Mbps, so efficient use of the bandwidth means the digital signal must be compressed. Using MPEG-2 compression, as many as 10 digital channels can be
squeezed in the 6 MHz space formerly occupied by one analog channel. This greater channel efficiency is the reason the FCC has mandated the conversion to digital TV. MPEG-2 is the same compression algorithm as DVD disks use. Although some slight decrease in quality results from the compression, it is hardly noticeable and it overcomes many of the impairments such as interference and ghosting that affect analog transmission.

Video Compression

Compression algorithms rely on the fact that a video signal contains considerable redundancy. Often large portions of background do not change between frames, but analog systems transmit these anyway. By removing redundancy, digital signal
processing can compress a video signal into a reasonably narrow bandwidth. The signal can be compressed to occupy as little as 64 Kbps, but the quality falls short, even for videoconferences, which need at least 384 Kbps, or six channels for reasonable quality. T1 bandwidth is needed for a signal that is approximately equal to the quality of a home VCR. Many standards, both public and proprietary have been developed for video compression. ITU’s H.261 is intended for videoconferencing, and is discussed later in more detail. The Motion Picture Experts Group, a working group of the International Organization for Standardization and the International Electrotechnical Commission, develops MPEG standards for encoding both video and audio. The principal standards of concern in telecommunications are MPEG-1,
-2, and -4. Other standards describe multimedia content and delivery. MPEG-1 compresses a video signal into bandwidths of up to 1.5 Mbps. The resolution is 288 lines per frame, which is home VCR quality. It is satisfactory for broadcast use if the scene does not have too much action. MPEG-2 codes studio quality
video into bit streams of varying bandwidth. The most popular studio signal, known as D-1 or CCIR 601, is coded at 270 Mbps and can be compressed into about 3Mbps. Scenes with high activity such as sports broadcasts require bit rates of about 5 or
6Mbps. MPEG-3 was intended for HDTV, but it was discovered that MPEG-2 syntax was sufficient. MPEG-4 is an enhancement for multimedia transmission. Video is compressed by predictive coding and eliminating redundancy. Flicking by at 30 frames per second, much in a moving picture does not change from frame to frame. Interframe encoding recognizes when portions of a frame remain constant, and transmits only the changed portions. Intraframe encoding provides another element of compression. The picture is broken into blocks of 16 Ч 16 pixels. Ablock is transmitted only when pixels within that block have changed. Otherwise, the decoding equipment retains the previous block and forwards it to the receiver with each frame. Predictive coding analyzes the elements that are changing, and predicts what the next frame will be. If the transmitting and receiving codecs both use the same prediction algorithm, only changes from the prediction must be transmitted, not the complete frame. Approximately every two seconds, the entire frame is refreshed, but in intervening frames, only the changed pixels are transmitted. The use of predictive coding requires a high-quality transmission facility. Lost packets in video-over-IP can have a detrimental effect beyond the information loss of one frame because of the predictive nature of the coding algorithm. Encoding systems are classified as lossless, or lossy. Information in a lossless coding system can be restored bit-for-bit. A lossy encoding system transmits only enough to retain intelligibility, but not enough to ensure the integrity of the received signal. Lossy systems work well for sending still scenes, but motion can cause a tiling or smearing effect as the receiving codec attempts to catch up with the transmitter. The higher the compression and the more vigorous the motion, the greater is the smearing effect.

High Definition Television (HDTV)

The present NTSC television standard was defined in 1941 when 525-line resolution was considered excellent quality and when such technologies as large-scale integration were hardly imagined. The standard was advanced for its time, but it is far from the present state of the art. Larger cities are running out of broadcast
channel capacity. Although not all channels are filled, co-channel interference prevents the FCC from assigning all available channels. Large television screens are becoming more the rule than the exception, and at close range the distance between scan lines is disconcerting. The 525 scan lines of broadcast television and the 4:3 width-to-height ratio of the screen, called its aspect ratio, limit picture quality. With wide-screen movies and the growing popularity of large-screen television sets, the definition of the current scanning system is considerably less than that of the original image. All of this leads to a transition to HDTV. HDTV has been introduced in most of the larger markets in the United States, but it has not been widely accepted yet because it requires replacement of existing television sets. Table 22-1 compares NTSC video with the new standard, which is known as Advanced Television Systems Committee (ATSC). The resolution of HDTV is far superior to NTSC. It has six times the number of pixels and supports wide screen television.

Video on Demand

A driving factor for digital television is video on demand (VoD). Today’s CATV systems deliver all channels to every residence, and unwanted or unauthorized channels are trapped out or scrambled. VoD refers to a broad spectrum of services that are delivered over a broadband medium. Entertainment, information, and education services are examples of VoD services that the service provider transmits on order. Subscribers can choose movies or programs they want via an onscreen menu, and control the sessions with VCR-like functions such as stop, fast-forward, and rewind. VoD may save a trip to the neighborhood video rental store, but the main question is delivery. The two principal delivery methods are via broadband cable or over DSL. Speed is the limiting factor with DSL. Reasonable quality can be obtained
with the popular ADSL, but studio quality HDTV requires at least 3Mbps, which requires VDSL. The limiting factor here is its range, which is about 4000 ft (1200 m). Delivery over cable is not too different from a range standpoint, however, to achieve the broadband speeds required without compromising quality, the streaming video signal must be brought to a neighborhood center over fiber. Cable providers offer VoD to digital service subscribers, which so far are a minority. Digital television sets are readily available, but for now most television sets are analog, which means a converter is required. Video servers can also be an obstacle. The amount of data that must be delivered to fill digital pipes to thousands of simultaneous users requires servers capable of storing many terabytes of data.

CABLE TELEVISION SYSTEMS

Cable television systems have three major components: headend equipment, trunk cable, and feeder and drop cable. Figure 22-3 is a block diagram of a conventional CATV system. All channels that originate at the headend are broadcast to all stations, which means the operator must scramble or block premium channels the user is not paying for. Headend equipment generates local video signals and receives signals from a variety of sources including off-the-air broadcasts, communication satellites, or microwave relay or fiber-optic connections from other providers. The analog signals from the headend are modulated to a channel within the bandwidth of the cable, which may be as great as 1 GHz. Headend equipment applies the signal to a trunk cable to carry the signal to local distribution systems. The trunk cable is equipped with broadband amplifiers that are equalized to carry the entire bandwidth. Amplifiers have about 20 dB of gain and are placed at intervals of approximately 500 m. Amplifiers known as bridgers couple the signal to feeder cables. Amplifiers contain automatic gain control circuitry to compensate for variations in cable loss. Power is applied to amplifiers over the coaxial center conductor. To continue essential services during power outages and amplifier failures, the cable operator provides redundant amplifiers and backup battery supplies. Because the CATV signals operate on the same frequencies as many radio services, the cable and amplifiers must be free of signal leakage since a leaking cable can interfere with another service or vice versa. As with other analog transmission media, noise and distortion are cumulative through successive amplifier stages. Analog impairments limit the serving radius of 70-channel CATV to about 8 km from the headend. Bridger amplifiers split feeder or distribution cable from the trunk cable. Multiple feeders are coupled with splitters or directional couplers, which match the impedance of the cables. The feeder cable is smaller and less expensive and has higher loss than trunk cable. Subscriber drops connect to the feeder cable through taps, which are passive devices that isolate the feeder cable from the drop. The tap must have enough isolation that shorts and opens at the television set do not affect other signals on the cable.

Hybrid Fiber Coax (HFC)

As cable technology improved, the bandwidth increased and more channels were added. Some operators added upstream channels to provide additional revenuegenerating services such as alarm monitoring, but the real revolution came with Internet access. Although the bulk of Internet traffic flow is downstream, a substantial amount of upstream bandwidth is needed. The conventional CATV model has either limited or no upstream bandwidth, and routing every channel past every subscriber does not work for Internet access because of the shared nature of the medium. As Internet traffic increases, the response time increases, generally in proportion to the number of subscribers. The answer is to rebuild cable networks with an HFC model similar to the one in Figure 22-4. Both entertainment and access bandwidth are brought to neighborhood centers on a fiber backbone. The entertainment channels are applied to the distribution cable as always, but the Internet channels are combined to a lesser number of subscribers. The response time on the shared portion of the bandwidth is limited by controlling the number of subscribers that a node serves. The HFC architecture gives cable companies control over shared bandwidth to make it suitable for other services. One logical candidate is telephone service. Once the cable infrastructure is in place, the incremental per-subscriber cost of VoIP is small. As shown in Figure 22-4, the IP bandwidth is delivered to a router at the headend. Voice packets are routed to a media gateway, which is controlled by a softswitch that can be located anywhere. This method of delivering telephone service has certain advantages that exist today by regulatory fiat, but may not persist. Congress has elected to exempt IP services from the many taxes and fees that it imposes on telephone service. Although it is impossible to foresee what Congress will do in the future, nothing suggests that this exemption is permanent. Another issue is exemption from equal access. Today the cable companies are not required to permit equal access to their facilities, which means competing service providers cannot rely on cable as an access medium. Either of these would affect the profitability of local telephone service over cable.

VIDEOCONFERENCING EQUIPMENT

Videoconferencing has considerable appeal, primarily as a substitute for travel, but it has yet to become a mainstream application. The primary drawback has been cost. Not long ago, the cameras, monitors, codec, and formal conference room setup could easily exceed $100,000 and the payback was difficult to quantify. Recently, equipment costs have dropped to a fraction of their previous levels and a conference unit can now be placed almost anywhere. The transmission costs, however, remain high. A reasonable videoconference requires 384 Kbps, or six BRI channels. Add usage costs to that and conferences, particularly multipoint conferences, are still expensive. A two-way videoconference over IP requires about 400 Kbps of full-duplex
bandwidth. With a stable private network in place, the quality is as good as ISDN. The Internet is not a suitable medium where true conference-quality video is required, so most external conferences will need an ISDN gateway.
A videoconference facility has some or all of the following subsystems integrated into a unit:
_ Video codec
_ Audio equipment
_ Video production and control equipment
_ Graphics equipment
_ Document hard copy equipment
_ Communications
A full description of these systems is beyond the scope of this book, but we will discuss them here briefly to illustrate the composition of a full videoconferencing facility. Personal video communications equipment is readily available and if the network has sufficient bandwidth and QoS, it is far less elaborate than a
formal conference facility, and will likely be the application that enables videoconferencing to fulfill its promise.

Video Codec

The codec converts the analog video signal to digital and compresses it for transmission. At the distant end the process is reversed. Codecs for dial-up conferences must support H.261. Many also support H.263 coding for IP conferences.

Audio Equipment

Most analysts believe that audio equipment is the most important part of a videoconference facility. In large videoconferences it is often impossible to show all participants, but it is important that everyone hear and be heard clearly. Audio equipment consists of microphones, speakers, and amplifiers placed strategically
around the room. Sometimes speaker telephones are used, but with less satisfactory results than codec audio. The codec robs a portion of the bandwidth to transmit the audio, so some products allow the operator to reduce the amount of audio bandwidth as a way of improving the video. When IP conferencing is used the
audio must be multiplexed on the bit stream because lip sync cannot be preserved with a separate audio channel.

Video and Control Equipment

Video equipment consists of two or three cameras and associated control equipment. The main camera usually is mounted at the front of the room and often automatically follows the voice of the speaker. Zoom, tilt, and azimuth controls are mounted on a console, where the conference participants can control them from a panel with a joystick. A second camera mounts overhead for graphic displays. The facility sometimes includes a third mobile camera that is operated independently. A switch at the console operator’s position selects the camera. Usually, one monitor shows the picture from the distant end and another shows the picture at the near end. In single-monitor conferences the near end can be
viewed in a window using the monitor’s picture-in-picture feature.
Digitizing and encoding equipment compresses full motion video or creates freeze-frames. In addition, encryption equipment may be included for security. Other equipment can freeze a full motion display for a few seconds while the participants send a graphic image over the circuit. Sometimes digital storage equipment
enables participants to transmit presentation material ahead of time so graphics transmission does not waste conference time.

Graphics Equipment

Videoconference facilities may include graphics-generating equipment to construct diagrams. Some systems provide desktop computer input so that tools in the computer can be used for generating graphics.

Communications

Digital communication facilities are required for videoconferences. ISDN is required for connections over the PSTN. Two 64 Kbps B channels and separate signaling channel provide enough bandwidth for an acceptable conference, but at least 384 Kbps is required for conference quality. Where an IP network with sufficient bandwidth and QoS is available, it is a good medium for conferences over the internal network. Frame relay is an excellent platform for videoconferencing if the access bandwidth is sufficient.

ITU-T H.320 Video Standards

Before the ITU-T H.320 standards were developed, manufacturers used proprietary standards, which meant that both ends of a videoconferencing session had to use the same equipment. Now, interoperability is assured by use of standards from the H.320 family. Table 22-2 lists the standards included under H.320. The amount of bandwidth supplied in the transmission facilities must be in multiples of 64 Kbps, known as P Ч 64 (pronounced P times 64). P can be from 1 to 30 64 Kbps channels; i.e. a single DS-0 up to full E1. Two options are offered. The full common intermediate format (CIF) offers frames of 288 lines by 352 pixels. This is approximately half the resolution of commercial television, which is 525 lines by 480 pixels. The second alternative is quarter CIF (QCIF), which is 144 lines by 176 pixels. The modulation method is the discreet cosine transform (DCT) algorithm.

H.323 Video Standards

The public Internet is not a sufficiently stable medium for reliable high-quality videoconferences, but for some it is good enough. Even better is the enterprise IP network or frame relay. The network can be designed with sufficient bandwidth and equipped with QoS protocols that make videoconferencing over IP an excellent alternative and considerably less costly than dial-up. We discussed H.323 signaling in Chapter 12. Those protocols work for either voice or video. The benefit of H.323 is its simplicity once it is set up and working. The standard RJ-45 Ethernet jack is ubiquitous, and can accept video without concern about how many channels are needed. A rollabout video unit can be hooked to any jack just like a laptop computer. One of the driving applications is desktop videoconferencing. The equipment is contained in a standard desktop computer that has a small video camera mounted on top of the monitor. The conferencing equipment is mounted on a board that plugs into a computer expansion slot, or it is an external box that plugs into a board in the computer. If the network is designed for video, the result is an economical method of conducting a personal videoconference. Conferences are spontaneous, with no need to schedule a conference room. The addition of a picture to the call allows the parties to pick up the nonverbal content of a session by seeing expressions. The screen is generally too small and the camera angle too narrow for group conferences, but for small groups it is excellent. Most products permit the users to share and view computer files over the network. As desktop video gains acceptance, it will be an effective tool for enhancing the quality of telephone calls and for enabling users to collaborate on files.

VIDEO APPLICATION ISSUES

Entertainment is likely to remain the primary driving force behind video into the future, but business, healthcare, and educational uses of television will be increasingly important. As CATV provides a broadband information pipeline into a substantial portion of American households, the growth of nonentertainment services
is expected.

Security

Television security applications take two forms—alarm systems and closed circuit television (CCTV) for monitoring unattended areas from a central location. Many businesses use CCTV for intrusion monitoring, and it is also widely used for intraorganizational information telecasts. Alarm services have principally relied on telephone lines to relay alarms to a center, which requires a separate line or automatic dialer. The expense of these devices can be saved by routing alarms over a CATV upstream channel, but to do so it requires a terminal to interface with the alarm unit. As described earlier, a computer in the headend scans the alarm terminals and forwards alarm information to a security agency as instructed by the user. H.323 video can also be used to deliver narrow-band IP video for security monitoring.

IP Services

Many CATV companies offer two-way data communications over their systems. As discussed in Chapter 8, the cable company allocates bandwidth for upstream and downstream using the DOCSIS protocol. VoD is delivered over IP bandwidth, using upstream channels to order services and control the delivery.

Control Systems

Two-way CATV systems offer the potential of controlling many functions in households and businesses. For example, utilities can use the system to poll remote gas, electric, and water meters to save the cost of manual meter reading. Power companies can use the system for load control. During periods of high demand, electric water heaters can be turned off and restored when reduced demand permits. A computer at the headend can remotely control a variety of household services such as appliances and environmental equipment. CATV companies themselves can use the system to register channels that viewers are watching and to bill for service consumed. They also can use the equipment to control addressable converters to unscramble a premium channel at the viewers’ request.

Opinion Polling

Experiments with opinion polling over CATV have been conducted. For example, CATV has been used to enable viewers to evaluate the television program they have just finished watching. The potential of this system for allowing viewers to watch a political body in action and immediately express their opinion has great
potential in a participatory democracy.

Streaming Video

The QoS requirements that may preclude using the Internet for the video transmission medium do not apply to streaming video. Enterprises can use the Internet for one-way broadcasts to employees and customers. Streaming video has endless
applications in training, education, entertainment, and other such purposes.

Videoconferencing

Companies that had never considered videoconferencing are investigating it more closely as the economics become more compelling. The first line of justification is generally replacement for travel, but as organizations adopt video as a way of doing business, the need for economic justification disappears. Videoconferencing makes it economical for more people to participate directly because travel is eliminated. A major advantage of videoconferencing where formal conference rooms are provided is scheduling. When users must reserve a facility, meetings must
begin and end on schedule, which is an added benefit.

Evaluation Considerations

As the cost of equipment drops, companies may find they have backed into the videoconferencing business without a plan. The result may be under-utilized equipment and network facilities, or the inverse, which is an overloaded network. Needs and expectations should be thoroughly assessed before embarking on
videoconferencing. The issues discussed in this section should be considered and the necessary controls imposed to increase the chances of success.

Type of Transmission Facilities

The initial issue to resolve is the telecommunications medium. BRI ISDN service is the default method where conferences use the PSTN. For higher bandwidths, inverse multiplexing may be required. Some units have the inverse multiplexer built in, while others use an external i-mux. Most digital PBXs can support PRI on the PSTN side and BRI toward the videoconferencing endpoints. Where IP bandwidth is available, H.323 video is an excellent alternative. The typical company in the market for H.323 video will have an existing internal network with spare capacity, or one to which capacity can be added inexpensively. Amajor advantage of IP conferencing is the fact that equipment can be relocated easily by plugging into a live Ethernet jack. The terminal equipment may be interchangeable for H.320 conferences. If external conferencing is required, a H.323-to-H.320 gateway will be required. If the video and audio signals are separate across the gateway, lip sync problems are apt to result.

Single- or Multipoint Conferences

Videoconferences are classed as point-to-point or multipoint. With terrestrial facilities, the distance and number of points served have a significant effect on transmission costs. Large companies with a significant amount of multipoint conferencing can often justify the cost of an MCU. Companies that use multipoint conferencing only occasionally can use bridging services offered by the major
IXCs. The IXCs offer “meet-me” conferencing in which conferees dial into a bridge. The control unit receives inputs from all locations, and sends each location the image that has seized the transmitting channel. The transmitting channel is allocated by one of three methods: under control of the conference leader, under
time control in which each location gets a share of the time, or by switching automatically to the location that is currently talking. The latter method is the most common, but it requires a disciplined approach.

Videoconferencing Equipment

The following issues should be evaluated in selecting videoconferencing equipment:
• Will the equipment used be videoconferencing appliances or PC-based?
• Will the conference be set up in formal conference rooms or from desktops?
• What level of quality is needed? Is a highly compressed signal satisfactory? Does the system offer full 30 frames per second or some lower factor?
• Can the system support multiple video formats (NTSC, SECAM, PAL)?
• Does the system support still graphics?
• How easily can information be brought into the conference? Is information sharing fundamental to the equipment or is it an add-on?
• Will fixed or portable equipment be used? Do the applications require frequent equipment relocation?
• Does audio ride on the video facility? Is wideband audio available?
• Is single-point or multipoint communication required? If multipoint, will the user supply its own multipoint control unit or use facilities offered by the IXC?

System Integration

Videoconference equipment is sometimes an assembly of units made by different manufacturers. To ensure compatibility, it is advisable to obtain equipment from a vendor who can integrate it into a complete system.

Security

The type of information being transmitted over the channel must be considered. If proprietary information is discussed during conferences, encryption of both video and audio signals may be required, particularly if IP is the transmission protocol.

Public or Private Facilities

Private videoconference facilities have a significant advantage over public access systems. Public facilities are unavailable in many localities, which may preclude holding many videoconferences. The travel time to a public facility offsets some
of the advantages of videoconference. Unless a private facility is used frequently, however, public facilities are usually the most cost-effective option.