System Y is the terminology used by BT, the main operator of the telephone network in the

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and North ...

, to refer to the

Ericsson (lit. "Telephone Stock Company of LM Ericsson"), commonly known as Ericsson, is a Swedish multinational networking and telecommunications company headquartered in Stockholm. The company sells infrastructure, software, and services in informat ...

AXE An axe ( sometimes ax in American English; see spelling differences) is an implement that has been used for millennia to shape, split and cut wood, to harvest timber, as a weapon, and as a ceremonial or heraldic symbol. The axe has ma ...

digital switching system. In the mid-1980s, British Telecom chose the well established AXE10 digital switch to provide competition for System X developed by a consortium of

Plessey The Plessey Company plc was a British electronics, defence and telecommunications company. It originated in 1917, growing and diversifying into electronics. It expanded after World War II by acquisition of companies and formed overseas compani ...

General Electric Company The General Electric Company (GEC) was a major British industrial conglomerate involved in consumer and defence electronics, communications, and engineering. The company was founded in 1886, was Britain's largest private employer with over 250 ...

(GEC) (companies later combined as GPT), STC and BT's state owned predecessor, the

GPO GPO may refer to: Government and politics * General Post Office, Dublin * General Post Office, in Britain * Social Security Government Pension Offset, a provision reducing benefits * Government Pharmaceutical Organization, a Thai state enterpris ...

. The newly privatised BT brought in Ericsson as a competitive alternative supplier ending Plessey/GEC's monopoly on the provision of switching systems. Initially, the AXE systems installed in the UK were partially locally manufacturered in partnership with

Thorn EMI Thorn(s) or The Thorn(s) may refer to: Botany * Thorns, spines, and prickles, sharp structures on plants * ''Crataegus monogyna'', or common hawthorn, a plant species Comics and literature * Rose and Thorn, the two personalities of two DC Comic ...

and later directly by Ericsson. While System X exchanges were more widespread in BT's network, AXE10 (and subsequent versions) remain common in the classic BT

PSTN 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 ...

until their eventual replacement when the network is closed, which at the time of the writing is expected to be in 2025 AXE10 covers two main types of

digital telephony Telephony ( ) is the field of technology involving the development, application, and deployment of telecommunication services for the purpose of electronic transmission of voice, fax, or data, between distant parties. The history of telephony is i ...

switching equipment: the remote subscriber switch (RSS) and the AXE10 local switch. RSS acts as a

remote concentrator In modern telephony a remote concentrator, remote concentrator unit (RCU), or remote line concentrator (RLC) is a concentrator at the lowest level in the telephone switch hierarchy. Subscribers' analogue telephone/PSTN lines are terminated on con ...

and deals with the conversion of analogue telephony signals used in the

access network An access network is a type of telecommunications network which connects subscribers to their immediate service provider. It is contrasted with the core network, which connects local providers to one another. The access network may be further ...

, which is the copper pairs between exchange buildings and customer premises, also called

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 ...

, and the multiplexing of customer lines over cabling to the AXE10 local switching unit. The AXE10 local switch uses a processor-controlled switch to route calls and data depending on the destination of the telephony transmission. BT's AXE10 network, which has been in service since 1986, is maintained in house by its own engineers although

still provide high-level support, software upgrades and repairs at component level. AXE/System Y, System X and other

TDM TDM may refer to: * ''TDM (film), TDM'', a 2023 Indian Marathi language, Marathi comedy film * TDM (Macau) (), a Macanese radio and television network * The Yamaha TDM, a motorcycle model * Target Disk Mode, a boot mode on certain Macintosh compute ...

technologies are already being be phased out as BT, in common with many networks around the world, implements its next generation access network, which will ultimately be based predominantly on fibre to premises (FTTP), with voice services provided using

VoIP 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 t ...

technology.

References

Telephone exchange equipment BT Group {{telephony-stub