User:Luis F. Gonzalez/Class 4 switch
From Wikipedia, the free encyclopedia
A Class 4 or Tandem switch is telephone company (telco) central office telephone exchange used for long distance communications in the Public Switches Telephone Network (PSTN) to interconnect telephone company offices. In contrast, a Class 5 switch is primarily used to terminate local calls, in other words connect to the customer.
Tandem is a telephony term meaning "to connect in series." It is also called a "TDM switch." Thus, a tandem switch connects telecommunications trunks. A tandem switch is an intermediate switch or connection between an originating telephone call or location, and the final destination of the call. A Tandem switch is a computer that is specialized for Time-division multiplexing (TDM)-based, circuit-switched telephone calls.
In the past, most of the accounting, billing management and call recording was handled by tandem switches, also called "toll switches." Subsequently, such services were taken over by end office switches.
[edit] Sector and Access Tandems
A sector tandem switconnects end offices for intra-LATA traffic.
An access tandem switch provides the connection between end-offices and the POPs for interexchange carriers (IXCs).
In the past, Class 4 tandem switches dealt only with high-speed, four-wire T1, T3 and OC-3 connections in contrast to two-wire local lines on Class 5 end-office switches. Subsequently, all switches were made to support four-wire lines.
Sector and Access Tandems The switches in the tandem offices in the center of each of the LATAs in this illustration are providing both traditional sector tandem services (intraLATA) between local end offices and access tandem services to IXCs (inter-LATA).
One Tandem Switch is the 4ESS, a Lucent Technology switch design for AT&T long distance communications. Currently, most Class 5 switches can conduct both local and long distance phone services. In other words, the functions of a Tandem switch are integrated into a Class 5 switch. Tandem switches from Nortel Networks (DMS).
Another telephone term for equipment and services that are non-customer facing. The telephone switch hierarchy nomenclature was coined by AT&T.
[edit] New
. A telephone company or centralized equal access provider switching system that provides a concentration and distribution function for originating or terminating traffic between end offices and a customer-designated premises. [NECA/ FCC-5] 2. An exchange carrier switching system that provides a traffic concentration and distribution function for inter-LATA traffic originating/terminating within a LATA. [T1.506-1989]
