AC Alternating Current

ACD Automatic Call Distribution

ADM Add/Drop Multiplexer

ADMCP Adaptive Differential Pulse Code Modulator

AMI Alternate Mark Inversion

ARS Automatic Route Selection

BH Busy Hour

BOC Bell Operating Company

bps Bits Per Second

BRI Basic Rate Interface

CO Central Office

Codec Coder/Decoder

CPE Customer Premises Equipment

CRC Cyclic Redundancy Checking

CSU Channel Service Unit

DC Direct Current

DID Direct Inward Dialling

DISA Direct Inward System Access

DLC Digital Loop Carrier

DPCM Differential Pulse Code Modulation

DSO (Digital Signal Level 0) a 64 Kbps signal

DS1 (Digital Signal Level 1) a 1.544 Mbps signal (T1 Carrier)

DS1C (Digital Signal Level 1C) a 3.152 Mbps signal

DS2 (Digital Signal Level 2) a 6.312 Mbps signal (T2 Carrier)

DS3 (Digital Signal Level 3) a 44.76 Mbps signal (T3 Carrier)

DS4 (Digital Signal Level 4) a 274.176 Mbps signal

DSn Digital Signal n, where n stands for any of the levels of the DS hierarchy: 0, 1, 1C, 2, 3, 4, ect.

DSU Data Service Unit

DTMF Dual-Tone MultiFrequency

E-Mail Electronic Mail

EMI Electromagnetic Interference

EO End Office

ESF Extended Superframe

FDDI Fiber Optic Distribution Data Interface

FDM Frequency Division Multiplexing

FT1 Fractional T1

FX Foreign Exchange Trunk

Gbps Gigabits Per Second

Giga Billion

Hz Hertz

IC Integrated Circuit

IEC Interexchange Carrier

IPM Impulse Per Minute

ISDN Integrated Services Digital Networks

kbps Kilobits Per Second

KSU Key System Unit

LATA Local Access and Transport Area

LCR Least Cost Routing

LEC Local Exchange Carrier

LED Light Emitting Diode

Mbps Megabits Per Second

MSA Metropolitan Statistical Area

MTSO Mobile Telephone Switching Offices

nm Nanometer

NRZ Non-Return to Zero

PAM Pulse Amplitude Modulation

PBX Private Branch Exchange

PCM Pulse Code Modulation

POP Point of Presence

POTS Plain Old Telephone Service

PRI Primary Rate Interface

PSTN Public Switched Telephone Network

RBOC Regional Bell Operation Company

RFI Radio Frequency Interference

RZ Return to Zero

SDS Space-Division Switching

SF Super Frame

SMDR Station Message Detail Recording

SONET Synchronous Optical Network

SP Signalling Point

SS7 Signalling System Point

STS Space-Time-Space

T1 DS1 (1:544 Mbps signal) carrier system

T2 DS2 (6:312 Mbps signal) carrier system

T3 DS3 (44.76 Mbps signal) carrier system

TDM Time-Division Multiplexing

TDS Time-Division Switching

TST Time-Space-Time

UCD Uniform Call Distribution

WATS Wide Area Telecommunication Service