Telecom

Sound Wave

Energy pattern that carries what humans hear through a medium

Transmission Medium

Material or space that carries sound waves from source to receiver

Solid Medium

Medium that carries sound through vibrations such as string copper or fiber

Liquid Medium

Medium that carries sound through water

Gas Medium

Medium that carries sound through air or radio frequency paths

Distance Limitation

Main limit of natural voice transmission before it becomes hard to understand

Telephony

Construction and operation of telephone systems used to transmit speech or sound between points

Sine Wave

Geometric waveform that oscillates periodically through nature

Sinusoidal Wave

Another name for a sine wave

Amplitude

Power or height of a wave that determines loudness or volume

Frequency

Number of sound waves that pass a fixed point in a unit of time

Hertz

Unit of frequency equal to one wave cycle per second

Pitch

How humans perceive sound frequency

Voice Frequency Range

Telephone voice range of 300 to 3400 Hz for clear human speech

Analogous

Continuous and smoothly changing like natural sound waves

Analog Telephony

System that uses copper wires to transmit voice and data as electronic pulses

Electrical Pulses

Signal changes used by analog telephony to represent sound over copper

Central Office

Switching hub that connects customers and trunks to other offices or carriers

CO

Abbreviation for Central Office

Trunk

Physical bundled connection or channel between switching locations or carriers

Trunking

Technique that lets multiple clients share circuits carriers channels or frequencies

Multiplexing

Modern term for combining multiple signals into one larger signal and separating them later

Rectifier

Central office power device that helps convert AC power to DC power

Inverter

Central office power device that converts DC power to AC power for auxiliary equipment

Storage Battery

Backup power source used by a central office during commercial power failure

Generator

Standby power source used by a central office for extended outages

Landline

Telephone line where signals travel through copper wire or optical fiber

Main Line

Another name for a landline

Fixed Line

Another name for a landline

Dedicated Landline

Private point to point landline reserved for one specific mission or emergency purpose

POTS

Legacy basic analog phone service over copper wires

Plain Old Telephone Service

Basic traditional analog landline service over copper wires

PSTN

Public switched telephone network that connects telephone calls through the larger phone network

Telephone Switchboard

Manual system where operators connected subscriber lines by hand

Automatic Telephone Switch

Switch that routes calls automatically based on digits dialed by the subscriber

Telephone Exchange

Central switch point where telephone lines exchange connections to route calls

Telephone Switch

Call routing device that controls the telephony network and decides where calls go

Telephone Set

Complete customer phone device used to speak hear and dial numbers

Physical Infrastructure

All physical cabling and systems between subscriber and switch

Backbone Cabling

Structured inter building and intra building cabling that carries telecommunication circuits

Distribution System

Network of frames and cabling that connects subscribers to the central office

MDF

Main distribution frame used as a major organized connection point in the central office

IDF

Intermediate distribution frame used to organize telephone connections in larger buildings

Protocols

Rules used for signaling priority tagging transport services and policing

SS7

ITU signaling protocol for traditional PSTN call setup teardown and advanced features

Signaling System No. 7

Out of band PSTN signaling protocol that coordinates call control separately from voice traffic

Digital Telephony

Transmission of voice as digital data instead of continuous analog waves

Digital Signal

Signal that transmits information using discrete values

Discrete

Distinct or separate values used to represent digital information

Binary Code

Representation of information using 0s and 1s

PCM

Digital scheme that converts analog telephony signals into digital format

Pulse Code Modulation

Process that samples analog amplitude and encodes it into binary pulses

Sampling

Measuring the analog signal at specific moments in time

Modem

Modulator demodulator device where PCM conversion can occur

ISDN

Digital standard that carries voice video data and other services over copper telephone lines

Integrated Services Digital Network

Set of communication standards for simultaneous digital services over traditional copper lines

B Channel

Bearer channel that carries user voice or data in ISDN

D Channel

Delta channel that carries ISDN call control information

BRI

Basic Rate Interface for smaller business and residential ISDN use

Basic Rate Interface

ISDN interface with two 64 Kbps B channels and one 16 Kbps D channel

PRI

Primary Rate Interface for larger networks with higher call volume

Primary Rate Interface

ISDN interface with twenty three 64 Kbps B channels and one 64 Kbps D channel

VTC

Live two way video and audio communication between different locations

Video Teleconferencing

Technology that simulates face to face meetings using real time video and audio

Codec

Device or process that encodes decodes compresses and decompresses audio and video

Encoder Decoder

Codec function that changes raw audio and video into digital bitstream and back

Compression Decompression

Codec function that reduces data size for transmission and restores it for viewing

GVS

DISA managed DoD platform for video teleconferencing services

Global Video Services

DoD VTC platform that manages sessions and supports interoperability

Video Portal

Core GVS interface used to initiate manage and optimize VTC sessions

Video Gateway

GVS device that bridges legacy room systems with modern video conferencing environments

GVS Application

Administrative GVS feature used for accounts events and basic reports

GVS Desktop Client

Software that lets a computer become a personal VTC endpoint

Human Operator

Person who manually connected calls on early telephone switchboards

Subscriber

Customer or end user who dials and uses a telephone line

Strowger Switch

First commercially successful automatic electromechanical telephone switch

Dial Pad

Base 10 digit dialing device used to send call routing pulses

Selector

System part in early switches that physically selected the call path

Series of Selectors

Multiple selectors used to route calls across multiple central offices

Circuit Switching

Call routing method using one dedicated path for the entire call

Dedicated Path

Reserved connection that stays active for the full duration of a circuit switched call

1ESS

First fully electronic telephone switch using solid state electronics and stored program control

Stored Program Control

CPU based software control that guided electronic telephone switching

Data Selectors

Digital line cards used in electronic switches for routing and multiplexing

TDM Trunk

Time division multiplexed trunk used to carry circuit switched voice

DMS

Northern Telecom fully digital switching system that used PCM for voice and control

Digital Multiplex System

PCM based digital telephone switch widely used by the DoD

Packet Switching

Method that sends voice or data as packets over an IP network instead of a dedicated circuit

Silence Suppression

VoIP technique that conserves bandwidth by sending payload mainly when voice is detected

Call Processing Server

Center of a VoIP phone system that sets up and terminates VoIP control connections

Call Manager

VoIP system brain that manages call setup call control and call termination

PBX

Small scale private switch owned by an organization for internal and external calling

Private Branch Exchange

Organization owned switch used to route internal calls and connect to outside trunks

Unified Communications

Platform that combines voice messaging and video

Call Routing

Process of directing a telephone call from caller to intended recipient

Tip and Ring

Two wire pair used in traditional telephone circuits