Subscriber trunk dialling (STD) (also known as subscriber toll dialling) is a 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. An old rotary telephone This article is about telephone technology. ... A telephone operator at work on a private switchboard A telephone operator is either a person who provides assistance to a telephone caller, usually in the placing of operator assisted telephone calls such as calls from a pay phone, collect calls (called reversed-charge calls in the UK), calls which... 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. ... In computer networking, trunking describes using multiple network cables or ports in parallel to increase the link speed beyond the limits of any one single cable or port. ...

The term "subscriber trunk dialling" is 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 ([2]) that the STD system was completed. The system required that each area have its own STD code which could be dialled by subscribers, and although they are now sometimes 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 (MCMLVIII) was a common year starting on Wednesday of the Gregorian calendar. ... Elizabeth II (Elizabeth Alexandra Mary Windsor; born 21 April 1926) is Queen of 16 sovereign states, collectively known as the Commonwealth Realms. ... Bristol (IPA: ) is a city, unitary authority and ceremonial county in South West England, 115 miles (185 km) west of London and located at With a population of 400,000, and metropolitan area of 550,000, it is Englands sixth, and the United Kingdoms ninth, most populous city... Edinburgh (pronounced ; Dùn Èideann () in Scottish Gaelic) is the capital of Scotland and its second-largest city. ... This page refers to the year 1979. ... 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. March 8 is the 67th day of the year in the Gregorian Calendar (68th in Leap years). ... 1963 (MCMLXIII) was a common year starting on Tuesday (the link is to a full 1963 calendar). ... London (pronounced ) is the capital city of England and the United Kingdom. ... Part of the Paris skyline with from left to right: Montparnasse Tower, Eiffel Tower, and in the background, towers of neighboring La Défense. ...

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. ...

External links

• 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.
• Archive news article from the BBC on the introduction of Subscriber Trunk Dialling.
• Article detailing how the original STD Codes were allocated.