Telecom Terms and Concepts

Introduction to terms

Telecom and Computers are merged to deliver data

Tele – distance Communications

Transfer of information from a transmitter to a receiver

Many parts come together to provide a path

Source

Sink

Some terms to know

TransmitterReceiverCircuit

LinkLine

TrunkChannelSwitch

Network

Transmitter

Also known as sender or source Originates the information transfer Samples include:

–Voice telephones–Data terminals–Host systems–Video cameras

Receiver

Also known as the sink Destination of the information transfer Samples include:

-Telephones

-Host computers

-Video Monitors

Circuit

A communications path, over an established medium, between two or more points, from end to end, between transmitter and receiver

Generally implies a logical connection over a physical path

May be for transport or access

Access Circuits

From customer premise to the edge of the carrier network

Transport Circuit

Employed at the core of the network for long-haul transmission

Some types of Circuits

Simplex – (one way) Half-duplex – (two way, but only one at a time) Full-duplex – (two way, at the same time)

Link

A two-point segment of an end-to-end circuit (e.g., from a terminal to switch)

Circuits generally consist of several links

Line

Several definitions can make this term confusing.

PBX – station line – connection between the PBX switch and the station users terminal equipment

Rate and Tariff (Telco) – line refers to the local loop connection from Telco CO (Central Office) to the user in support of CPE (Customer Premise Equipment)

Lines in Telco-speak

Examples– Single phone line to a business– A multi-line set

Usually voice grade – although this is changing as the infrastructure matures

For Telco’s the line side is the users access to the network – for the other side there are Trunks

Trunk

A communications circuit, available to share among multiple users, on a pooled basis with contention managed by an intelligent switching device.– NOTE: this is not the same switching device as in a

Local Area Network – i.e. Layer 2

Trunks Connect Switches

Tie Trunks – connect PBX switches in a private, leased line network

Central Office Exchange Trunks – connect PBX’s to Telco switches

Interoffice Trunks – Connect CO Exchange groups

Trunk Groups

Groups of trunks serving the same special purpose.– WATS (Wide Area Telecommunications Service– DID (Direct Inward Dial)

Trunks are Directional

One way out -- Originating One way in -- Terminating Two-way – Combination

Channel

A means of communication between transmitter and receiver

A logical connection over a physical circuit to support a conversation

Switch

Establishes, maintains and changes logical connections over physical circuits– Circuit– Packet– Frame– Cell

Edge Switches

Positioned at the edge of the network Users gain access via an access link

Core Switches

Also known as Tandem Switches High capacity switches at the core to

interconnect edge switches

Network

The fabric of elements which work together to support the transfer of information