Glossary

Answer Connect Telecommunications Glossary An excellent telecommunications glossary.

These brief definitions should help you understand many of the terms used on this site.

Alternate media

Any media that allows telecommunications carriers to provide service to a customer. This includes, but is not limited to, fixed wireless (including satellite) and independent fiber optic lines.

Blocking

If a call or connection can not be completed, for any reason, it is said to be blocked.

CCS (Centa Call Seconds)

Used to indicate the number of seconds of telecommunications traffic, in an hour. 1 CCS = 100 seconds of traffic.

CO (Central Office)

The switch that connects customers to the local exchange carrier.

CLEC (Competitive Local Exchange Carrier)

A carrier that competes with the ILEC (see ILEC).

Erlang

Hours of telecommunications traffic, in an hour. For example, 1 Erlang means a line was in use for an hour. To support 12 Erlangs, you would need 12 lines.

Erlang B

A formula that calculates the expected blocking for a network, based on the traffic and number of lines. For example, P.05 means that approximately 5% of the calls would be blocked.

Erlang C

A formula that calculates the expected blocking for a network, and assumes callers will wait forever to get through (see Erlang B).

ILEC (Incumbent Local Exchange Carrier)

The local telephone company that connects customers to the central office.

Initial Installation

The installation of a brand new connection from the central office to the customer site. This may be installation of new lines (copper or fiber optic), or reuse of existing lines.

Kbps (Kilo bits per second)

Thousands of bits per second. Many voice channels use 64Kbps.

LEC (Local Exchange Carrier)

A telephone company that connects customers to the central office.

Mbps (Mega bits per second)

Millions of bits per second.

OC1

A fiber optic line carrying 155Mbps of voice or data. Equivalent to T3.

Survivable Link

A connection that can carry telecommunications traffic when the primary connection is unusable.

T1

A high speed, four wire, line that can carry 24 voice conversations, or 1.536Mbps of data.

T2

Equivalent to 4 T1s

T3

Equivalent to 28 T1s

Another resource for telecommunications definitions is Newton's Telecom Dictionary.