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Teleco Switches

A Telco switch is a large-scale computer system that is used to switch TDM-based, circuit-switched telephone calls. Also called a "voice switch".

Lucent and Nortel Networks are the primary vendors of this equipment. The main switching technology includes:

End office switch
Tandem switch
DMS
ESS

End Office Switch

An End Office Switch is a telephone central office switch that connects directly to the customer. It is also referred to as a "Class 5 switch" or "TDM switch". The computer is specialized for TDM-based, circuit-switched telephone calls. It handles services such as call forwarding and call waiting. Primary vendors include Lucent and Nortel Networks. See ESS and DMS.

Most of the call recording and billing is also performed in Class 5 end office switches, previously handled in Class 4 tandem switches.

Local telephone companies use both end office and tandem switches, which may be the exact same hardware with services differentiated only by software.

Tandem Switch

A Tandem Switch is also referred to as a "Class 4 switch" or "TDM switch. It is the older version of and End Office Switch, commonly known as a central office switch that links telco end offices together and does not connect to the customer directly.

It is a computer specialized for TDM-based, circuit-switched telephone calls.

Primary vendors include Lucent and Nortel Networks. See ESS and DMS.

Sector and Access Tandems

A sector tandem switch connects end offices for intraLATA traffic, while an access tandem switch provides the connection between end offices and the POPs for interexchange carriers (IXCs).

Previously, Class 4 tandem switches dealt only with high-speed, four-wire T1, T3 and OC-3 connections, compared to Class 5 end office switches supporting only two-wire local lines. Today, all switches support four-wire lines.

DMS (Digital Multiplex System)

A digital switch from Nortel Networks used in a telephone company central office. It includes:

Large local/toll exchange DMS-100/200
Small local exchange DMS-10
DMS-250 long distance switch
DMS-300 international gateway
DMS-500 local and long distance switch
DMS-100 wireless
DMS-Global Services Platform (GSP)
DMS-Programmable Services Architecture (DMS-PSA)
Advanced signaling solutions - including the DMS-STP and BroadBand STP.

ESS (Electronic Switching System)

A large-scale Lucent computer used to route telephone calls in a telephone company office.

The 5ESS is a Class 5 central office switch, and the 4ESS is a Class 4 tandem office switch. Also See SS7, Class 4 switch, Class 5 switch and digital cross-connect.

Next: Telco Call Detail Records [CDRs]