Subscriber trunk dialling (STD) (also known as Subscriber toll dialling) is an obsolete term for the UK telephone system allowing subscribers to dial trunk calls without operator assistance. The introduction in the UK of subscriber dialling of long distance calls removed the distinction that had existed between Trunk and Toll calls. This term however, is still widely prevalent in India to describe any national call made other than one's local unit. A "subscriber" is someone who subscribes to, i.e. rents, a telephone line and a "trunk call" is one made over a trunk line, i.e. a telephone line connecting two exchanges a long distance apart. Now that all calls may be dialled direct, the term has fallen into disuse. Obsolescence is when a person or object is no longer wanted even though it is still in good working order. ... This article needs to be cleaned up to conform to a higher standard of quality. ... This article is about operators in mathematics, for other kinds of operators see operator (disambiguation). ... In the US, under the purview of the Bell system, local telephone calls were free and the term toll was adopted for long distance calls because they were subject to a toll. ... For computer networking, trunking describes using multiple network cables/ports in parallel to increase the link speed beyond the limits of any one single cable or port. ...

The term "subscriber trunk dialling" is, or was, also used in other countries such as Australia, but the corresponding term in the US and Canada is direct distance dialing. The North American Numbering Plan (NANP) is a system for three-digit area codes that direct telephone calls to particular regions on a public switched telephone network (PSTN), where they are further routed by the local network. ... Direct Distance Dialing was a telephony innovation that enabled subscribers to call long distance numbers (Those outside the local exchange) without having to go though an operator. ...

In the UK, STD started when, on 5 December 1958, the Queen, who was in Bristol dialled a phone call to Edinburgh ([1]). However, it was not until 1979 that the STD system was completed ([2]). The system required that each area have its own STD code which could be dialled by subscribers, and although they are now officially called area codes, it is still common to see and hear the old term in everyday use. December 5 is the 339th day (340th in leap years) of the year in the Gregorian calendar. ... 1958 was a common year starting on Wednesday of the Gregorian calendar. ... The British monarch or Sovereign is the monarch and head of state of the United Kingdom and its overseas territories, and is the source of all executive, judicial and (as the Queen-in-Parliament) legislative power. ... Bristol is an English city and county and one of the two administrative centres of South West England (the other being Plymouth). ... Edinburghs location in Scotland Edinburgh viewed from Arthurs Seat. ... 1979 is a common year starting on Monday. ... A telephone numbering plan is a system that allows subscribers to make and receive telephone calls across long distances. ...

The term was extended, when on 8 March 1963, London subscribers were able to dial Paris direct using international subscriber trunk dialling ([3]). March 8 is the 67th day of the year in the Gregorian Calendar (68th in Leap years). ... 1963 was a common year starting on Tuesday (link will take you to calendar). ... St. ... The Eiffel Tower has become a symbol of Paris throughout the world. ...

In India the term still applies and to dial out of one's unit area, the relevant city code has to be prefixed to the local number. This prefix starts with a 0. Certain numbers are also prefixed with 95 which are local calls within 500 km.

See also

UK telephone numbering plan The UK telephone numbering plan, also known as the National Numbering Plan, is regulated by the Office of Communications (Ofcom), which replaced the Office of Telecommunications (Oftel) in 2003. ...

References

http://www.btplc.com/Corporateinformation/BTArchives/history/Eventsintelecommunicationshistory.htm

The archives of BT including archives of its predecessor organizations. A good source of information relating to the history of the telephone system in the UK.

http://news.bbc.co.uk/onthisday/hi/dates/stories/may/21/newsid_2510000/2510289.stm

Archive news article from the BBC on the introduction of Subscriber Trunk Dialling.

http://www.sigtel.com/tel_hist_earlystd.html

Article detailing how the original STD Codes were allocated.