{{No footnotes, date=August 2008 A class-5 telephone switch is a

telephone exchange telephone exchange, telephone switch, or central office is a telecommunications system used in the public switched telephone network (PSTN) or in large enterprises. It interconnects telephone subscriber lines or virtual circuits of digital syste ...

in the

public switched telephone network The public switched telephone network (PSTN) provides infrastructure and services for public telecommunication. The PSTN is the aggregate of the world's circuit-switched telephone networks that are operated by national, regional, or local teleph ...

(PSTN) that directly serves

subscriber The subscription business model is a business model in which a customer must pay a recurring price at regular intervals for access to a product or service. The model was pioneered by publishers of books and periodicals in the 17th century, an ...

s and manages subscriber calling features. Class-5 services include basic dial-tone,

calling features Calling may refer to: * Religious calling, a religious vocation * Effectual calling, a theological term * Vocation, or occupation * Audible animal communication, including mate calling and territorial threat sounds * Game call, a device that is ...

, and additional digital and data services to subscribers connected to a

local loop In telephony, the local loop (also referred to as the local tail, subscriber line, or in the aggregate as the last mile) is the physical link or circuit that connects from the demarcation point of the customer premises to the edge of the common ...

Function

A class 5 switch provides telephone service to end customers locally in the exchange area, and thus it is concerned with "subscriber type" activities: generation of dial-tone and other "

comfort noise Comfort noise (or comfort tone) is synthetic background noise used in radio and wireless communications to fill the artificial silence in a transmission resulting from voice activity detection or from the audio clarity of modern digital lines. S ...

s"; handling of network services such as advice of duration and charge etc. Specifically, a class-5 switch provides dial tone, local switching and access to the rest of the network. Class-4 switches do not provide subscriber lines, their role is to route calls between other switches. Typically a class-5 switch serves an area of a city, an individual town, or several villages and could serve from several hundred to 100,000 subscribers. Since the replacement of

electromechanical In engineering, electromechanics combines processes and procedures drawn from electrical engineering and mechanical engineering. Electromechanics focuses on the interaction of electrical and mechanical systems as a whole and how the two systems ...

exchanges by modern digital ones, the function of a class-5 switch in rural areas is often performed by a remote switch or Remote Digital Terminal installed at the original switch site to handle local switching or concentration, respectively. The class-5 switching infrastructure is then physically located in a larger population center. Urban areas with extensive underground plant tend to keep the classic class-5 office architecture.

Hardware

Before the office classification system for

Direct Distance Dialing Direct distance dialing (DDD) is a telecommunication service feature in North America by which a caller may, without operator assistance, call any other user outside the local calling area. Direct dialing by subscribers typically requires extra d ...

(DDD) was established, the principal designs in use for class 5 in the US were crossbar systems,

Panel switch The Panel Machine Switching System is a type of automatic telephone exchange for urban service that was used in the Bell System in the United States for seven decades. The first semi-mechanical types of this design were installed in 1915 in Newark, ...

es, and Strowger-type step-by-step systems. The DDD program involved installations of large numbers of new 5XB crossbar switches in the 1950s and 1960s. In addition,

1ESS switch The Number One Electronic Switching System (1ESS) was the first large-scale stored program control (SPC) telephone exchange or electronic switching system in the Bell System. It was manufactured by Western Electric and first placed into ser ...

es and their variants appeared in the 1960s. Most of these systems were removed in the late 20th century, primarily replaced in North America by DMS-10, DMS-100 and 5ESS switches in the Bell operating territories and the

GTD-5 EAX The GTD-5 EAX (General Telephone Digital Number 5 Electronic Automatic Exchange) is the Class 5 telephone switch developed by GTE Automatic Electric Laboratories. This digital central office telephone circuit switching system is used in the f ...

in the GTE operating areas. Principal European products include Ericsson

AXE telephone exchange The AXE telephone exchange is a product line of circuit switched digital telephone exchanges manufactured by Ericsson, a Swedish telecom company. It was developed in 1974 by Ellemtel, a research and development subsidiary of Ericsson and Televe ...

, Siemens

EWSD The Elektronisches Wählsystem Digital (EWSD), translated to ''Electronic Digital Switching System'' in English, is a widely installed German telephone exchange system, originally introduced in 1975 by Siemens AG, but discontinued in 2017. EWSD ...

and

Alcatel-Lucent Alcatel–Lucent S.A. () was a French–American global telecommunications equipment company, headquartered in Boulogne-Billancourt, France. It was formed in 2006 by the merger of France-based Alcatel and U.S.-based Lucent, the latter being a su ...

S12 and E10. In the 21st century, US and European service providers continued to upgrade their networks, replacing older DMS-10, DMS-100, 5ESS, GTD-5 and EWSD switches with

Voice over IP Voice over Internet Protocol (VoIP), also called IP telephony, is a method and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. The terms Internet ...

technology.

Function

Hardware

See also