Subscriber trunk dialling

Switching systems to enable automatic dialling of long distance calls by subscribers were introduced in the United Kingdom on 5 December 1958.

[2] The term 'STD call' was once commonly used in the UK, Ireland, Australia, India, and parts of Southeast Asia, but it may be considered archaic today, or possibly even no longer be understood.

The term subscriber trunk dialling is used in the United Kingdom, the Republic of Ireland, Australia, India and South East Asia.

This term however, is still widely prevalent in India to describe any national call made outside one's local unit.

Calls to Northern Ireland are now made by dialling 048 and the eight-digit local number, omitting the 028 STD code.

Examples were: These legacy codes dialled directly into Irish cities that had crossbar switching in the 1950s and 1960s, and predated the introduction of ISD in the UK.

The Irish STD system evolved around the introduction of LM Ericsson ARM and ITT Pentaconta crossbar trunk/tandem switches, and did not use the UK's director approach.