Editing Subscriber trunk dialling (section)

===Numbering plan===
In subscriber trunk dialing, each designated region of a country is identified by a unique numerical code (the STD code) that must be dialed as a prefix to each telephone number when placing calls.

Each city with a [[Director telephone system|director system]] was assigned a three-digit code, in which the second digit corresponded to the first letter of the city name on the telephone dial, except London which had the two-digit code 01. Codes were later changed (e.g., London became 020, and Manchester 0161).
*01 London
*021 Birmingham
*031 Edinburgh
*041 Glasgow
*051 Liverpool
*061 Manchester