principles of voice & data lesson 1: telephony essentials bellevue community college bob young,...

Principles of Voice & Data

Lesson 1:

Telephony Essentials

Bellevue Community College

Bob Young, Instructor

Terms & Explanations

PSTN

Public Switched

Telephone Network


POTS"Plain Old Telephone Service"

as in, "POTS line."


Phone PartsTransmitter - Mouthpiece

Receiver - Earpiece


Full Duplex - voice can be sent in both directions at the same time.

Half Duplex - voice can be sent in one direction at a time.


C.O. or COCentral Office


CPE• Customer Premise Equipment

• CPE may be owned by the telco or by the customer


The "Last Mile"

From the CO to the CPE


Outside Plant• Telco equipment between

the CO and the customer

• Poles, lines, vaults, etc.


On HookThe phone's handset

is in the cradle.Open loop condition -

no loop current.


Off HookThe phone's handsetis out of the cradle.

Closed loop condition -loop current is present.


RBOC• Regional Bell Operating

Company

• 1984 - Divestiture of AT&T

• Formation of 7 RBOC's

The Seven RBOCS:

1) Ameritech

2) Bell Atlantic

3) BellSouth

4) NYNEX

5) Pacific Bell

6) Southwestern Bell

7) US WEST

RBOC Map, 1984


BOC• Bell Operating Company

• Smaller, regional companies within the RBOC's– (22 BOC's)


IXCInterexchange Carrier

After divestiture, IXC's handled long distance calls


LECLocal Exchange Carrier


LATALocal Access and Transport

Area


ILECIncumbent Local Exchange

Carrier


CLECCompeting (or Competitive)

Local Exchange Carrier


British Terms• GPO - General Post Office

• BPO - British Post Office

• BT - British Telecom


ITUInternational

Telecommunications Union


ITU-TInternational

Telecommunications Union - Telecommunications

Standardization Sector


Tandem OfficeA central office unit used

primarily as an intermediate switching point for traffic

between local central offices within the tandem area


Toll TandemA central office unit used as the switching point between local CO traffic and toll (long

distance) traffic


EOEnd Office

A Central Office that connects directly to subscribers


Switches - Class 5• An End Office switch

• Provides local loop connections

• Call signaling and control - setup and knockdown


Switches - Class 4• A tandem switch

• Capable of connecting Class 5 switches


Switches - Class 3• A toll traffic switch

• Connects LEC's

• Capable of connecting Class 4 & 5 switches


PCMPulse Code Modulation

-law (North America & Japan)A-law (all other countries)8 KHz sampling rate


PCM Issues• Unrepresentative Sample

• Lack of Information

• Too Much Information


POP, PoPPoint of Presence

POIPoint of Interconnection


FXForeign Exchange

FXO - Foreign Exchange Office

FXS - Foreign Exchange Station


PBXPrivate Branch Exchange


KSUKey Service Unit

or

Key Switching Unit


DIDDirect Inward Dialing

as in, "DID Trunk"


DODDirect Outward Dialing

as in, "DOD Trunk"


Centrex ServiceA telco service in which the

PBX hardware and functionality is provided and

maintained by the telco


Analog Loop StartThe call is originated by going

off hook. Loop current initiates the call sequence.


E & M Trunks• Voice and signaling are

carried on separate wires

• E = "Ear"

• M = "Mouth"


Ground-Start TrunksThe call sequence is initiated

by grounding either the tip (from CO) or the ring wire

(from PBX)


DSHDigital Signal Hierarchy

• DS0, DS1, DS3• T1, T3• T1 = 1.544 Mbps


SF & ESFSuper Frame (D4)

Extended Super Frame


E-Carrier• Europe uses E1's instead of T1's

• E1 = 2.048 Mbps


SONETSynchronous Optical Network• North American Standard• Compare with SDH• STS-1 = 51.84 Mbps


STS & OCSynchronous Transport Signal

Optical CarrierExact same data rates

Know both terms


STS-1 = OC-1 = 51.84 Mbps

STS-2 = OC-2 = 103.68 Mbps

STS-3 = OC-3 = 155.52 Mbps

etc.

SONET Physical Hierarchy

SONET Architecture

SONET Ring


SONET & OSI ModelOSI Layer 1 Standard

(Physical Layer)


More SONET InfoSONET can be used for:

ATM

Gigabit Ethernet


SDHSynchronous Digital Hierarchy• International Standard• Don't confuse with DSH• STM-1 = 155.52 Mbps


155.52 Mbps

STS-3OC-3

STM-1


A & B Bit Signaling• Digital equivalent of analog

line signals

• Status of bits indicates idle or busy (on-hook, off-hook)

Stratum Clocks


Types of TimingAsynchronous

Synchronous

Plesiosynchronous


CSU/DSUChannel Service Unit

Data Service Unit


SWC, WCService Wire Center

Wire Center


Distribution Frame

Permanent wiring set up for easy cross connection


MDFMain Distribution Frame

Typically at CO or large PBX


IDFIntermediate Distribution

Frame

Typically outside plant or customer premise


CDFCombined Distribution Frame

Vertical blocks - CO linesHorizontal blocks - inside lines


MPOEMinimum Point of Entry

Demarcation Point

(Demarc)


NIDNetwork Interface Device


Load CoilsReduces line loss

Matches impedanceAnalog circuits only -

Can't use in digital circuits


Bridge Tap• Allows a cable to be run to

more than one location

• Each circuit can only be used at one location


Call Processing• Call setup

• Call maintenance

• Call completion (knockdown)

Call Signaling• Dial tone - 350 Hz and 440 Hz at –12 dBm

• Pulse dialing - (10 pps standard) 40msec make, 60msec break, 600msec pause

• DTMF - (23 pps standard)

• Ring - (80-90 VAC at 20 Hz)

• Ringback - 440 Hz and 480 Hz at –20dBm, 0.2 sec on, 0.4 sec off

• Busy - 480 Hz and 620 Hz, 0.5 sec on, 0.5 sec off

Analog Problems

• Loss

• Echo

• Noise

• Crosstalk

• Delay


Echo Cancellation• Acoustic Echo Control

(wireless networks)

• Far End Echo Cancellation

• (long distance, satellite)

principles of voice & data lesson 1: telephony essentials bellevue community college bob young,...

Documents

terms explanationsbocbell

local central offices

open loop condition

intermediate switching

half duplex voice

principles of voice

tandem switchcapable

pots line