Inland (UK) Switching
	In the 21st century, virtually all (UK) telephone and data traffic is processed by digital switches. In this section we look back to a time when Strowger, Crossbar and Electronic switching carried the bulk of the calls... We also find out about the development of Subscriber Trunk Dialling (STD) which greatly simplified the call set-up process.
| EXIT | Inland (UK) Switching | The Story of STD | Telegraphs & Telex | Mobile Exchanges | Recorded Information Services |

Exchange Types

In the 21st century, virtually all (UK) telephone and data traffic is processed by digital switches. In this section we look back to a time when Strowger, Crossbar and Electronic switching carried the bulk of the calls...

Once, all switching equipment used electro-mechanical switches to connect telephone calls. The Strowger system used a step-by-step process to route calls through the exchange. The Crossbar system used cross-point switches with marker control and lots of relays. Even the replacement electronic systems used reed-relays, until the solid-state System X and System Y switches were introduced in the late 1970s.

The Story of Subscriber Trunk Dialling (STD)

Prior to December 1958, only local calls (within a few miles of a town) could be directly dialled; all long distance or trunk calls had to be connected via an operator. All medium sized towns had their own operator or Auto-Manual Centre (AMC) at which the calls were received, connected and charged for; a very labour intensive process, which typically employed hundreds of staff at each location. Subscriber Trunk Dialling (STD) was progressively introduced, but it was not until 1979, that it covered the whole of the UK. So it was that the period from 1960 to 1980 saw the transition from part manual to fully automatic switching of inland calls. 

	Here we follow the progress of switching and numbering from the very first STD call in 1958 as the demand for calls grew and the telephone network developed from a manual system to a fully automatic one.

Telegraphs & Telex

This section will take a look at the automation of the Telegraph Services from the late 1930s onwards and their evolution into Telex and Datel which were the forerunners of today's dial-up and high speed data links.

Mobile Exchanges

	Over the years, a variety of mobile exchanges were built to provide extra exchange capacity where it was most needed and to give emergency cover in the event of a disaster. Typical equipments fitted ranged from special UAX variants, Non-Director to TXE2 as well as containerised Digital and customer switch replacement modules.