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

Terms & Explanations

POTS"Plain Old Telephone Service"

as in, "POTS line."

Terms & Explanations

Phone PartsTransmitter - Mouthpiece

Receiver - Earpiece

Terms & Explanations

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.

Terms & Explanations

C.O. or COCentral Office

Terms & Explanations

CPE• Customer Premise Equipment

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

Terms & Explanations

The "Last Mile"

From the CO to the CPE

Terms & Explanations

Outside Plant• Telco equipment between

the CO and the customer

• Poles, lines, vaults, etc.

Terms & Explanations

On HookThe phone's handset

is in the cradle.Open loop condition -

no loop current.

Terms & Explanations

Off HookThe phone's handsetis out of the cradle.

Closed loop condition -loop current is present.

Terms & Explanations

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

Terms & Explanations

BOC• Bell Operating Company

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

Terms & Explanations

IXCInterexchange Carrier

After divestiture, IXC's handled long distance calls

Terms & Explanations

LECLocal Exchange Carrier

Terms & Explanations

LATALocal Access and Transport

Area

Terms & Explanations

ILECIncumbent Local Exchange

Carrier

Terms & Explanations

CLECCompeting (or Competitive)

Local Exchange Carrier

Terms & Explanations

British Terms• GPO - General Post Office

• BPO - British Post Office

• BT - British Telecom

Terms & Explanations

ITUInternational

Telecommunications Union

Terms & Explanations

ITU-TInternational

Telecommunications Union - Telecommunications

Standardization Sector

Terms & Explanations

Tandem OfficeA central office unit used

primarily as an intermediate switching point for traffic

between local central offices within the tandem area

Terms & Explanations

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

distance) traffic

Terms & Explanations

EOEnd Office

A Central Office that connects directly to subscribers

Terms & Explanations

Switches - Class 5• An End Office switch

• Provides local loop connections

• Call signaling and control - setup and knockdown

Terms & Explanations

Switches - Class 4• A tandem switch

• Capable of connecting Class 5 switches

Terms & Explanations

Switches - Class 3• A toll traffic switch

• Connects LEC's

• Capable of connecting Class 4 & 5 switches

Terms & Explanations

PCMPulse Code Modulation

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

Terms & Explanations

PCM Issues• Unrepresentative Sample

• Lack of Information

• Too Much Information

Terms & Explanations

POP, PoPPoint of Presence

POIPoint of Interconnection

Terms & Explanations

FXForeign Exchange

FXO - Foreign Exchange Office

FXS - Foreign Exchange Station

Terms & Explanations

PBXPrivate Branch Exchange

Terms & Explanations

KSUKey Service Unit

or

Key Switching Unit

Terms & Explanations

DIDDirect Inward Dialing

as in, "DID Trunk"

Terms & Explanations

DODDirect Outward Dialing

as in, "DOD Trunk"

Terms & Explanations

Centrex ServiceA telco service in which the

PBX hardware and functionality is provided and

maintained by the telco

Terms & Explanations

Analog Loop StartThe call is originated by going

off hook. Loop current initiates the call sequence.

Terms & Explanations

E & M Trunks• Voice and signaling are

carried on separate wires

• E = "Ear"

• M = "Mouth"

Terms & Explanations

Ground-Start TrunksThe call sequence is initiated

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

(from PBX)

Terms & Explanations

DSHDigital Signal Hierarchy

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

Terms & Explanations

SF & ESFSuper Frame (D4)

Extended Super Frame

Terms & Explanations

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

• E1 = 2.048 Mbps

Terms & Explanations

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

Terms & Explanations

STS & OCSynchronous Transport Signal

Optical CarrierExact same data rates

Know both terms

Terms & Explanations

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

Terms & Explanations

SONET & OSI ModelOSI Layer 1 Standard

(Physical Layer)

Terms & Explanations

More SONET InfoSONET can be used for:

ATM

Gigabit Ethernet

Terms & Explanations

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

Terms & Explanations

155.52 Mbps

STS-3OC-3

STM-1

Terms & Explanations

A & B Bit Signaling• Digital equivalent of analog

line signals

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

Stratum Clocks

Terms & Explanations

Types of TimingAsynchronous

Synchronous

Plesiosynchronous

Terms & Explanations

CSU/DSUChannel Service Unit

Data Service Unit

Terms & Explanations

SWC, WCService Wire Center

Wire Center

Terms & Explanations

Distribution Frame

Permanent wiring set up for easy cross connection

Terms & Explanations

MDFMain Distribution Frame

Typically at CO or large PBX

Terms & Explanations

IDFIntermediate Distribution

Frame

Typically outside plant or customer premise

Terms & Explanations

CDFCombined Distribution Frame

Vertical blocks - CO linesHorizontal blocks - inside lines

Terms & Explanations

MPOEMinimum Point of Entry

Demarcation Point

(Demarc)

Terms & Explanations

NIDNetwork Interface Device

Terms & Explanations

Load CoilsReduces line loss

Matches impedanceAnalog circuits only -

Can't use in digital circuits

Terms & Explanations

Bridge Tap• Allows a cable to be run to

more than one location

• Each circuit can only be used at one location

Terms & Explanations

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

Terms & Explanations

Echo Cancellation• Acoustic Echo Control

(wireless networks)

• Far End Echo Cancellation

• (long distance, satellite)