The Director System was introduced to six cities in the UK with the advent of the automatic telephone exchange. It involved a device (the director) which received dialled digits and automatically translated them to route calls between exchanges in the city. Directors were applied to step-by-step switching equipment; crossbar and electronic switches had such capabilities built into them.

Each city was given a 3 digit code where the second digit corresponded to the first letter of the cities name on the telephone dial, with the exception of London which was given a 2 digit code "01":

• 01 London
• 021 Birmingham
• 031 Edinburgh
• 041 Glasgow
• 051 Liverpool
• 061 Manchester

Each subscriber was then given a 7 digit number where the first 3 digits corresponded to the local exchange. Again, this was done by linking each number on the telephone dial to letters:

• 1
• 2 ABC
• 3 DEF
• 4 GHI
• 5 JKL
• 6 MN
• 7 PRS
• 8 TUV
• 9 WXY
• 0 OQ

For example a number of in Wimbledon 1234 would equate to 01 WIM 1234 or 01 946 1234.

The system had little scope for expansion and had to be dropped in favour of all figure dialling in 1966.

Calls from Ireland

Until 1992, calls to these cities from Ireland were made using the following codes:

• 031 London
• 032 Birmingham
• 033 Edinburgh
• 034 Glasgow
• 035 Liverpool
• 036 Manchester

In that year, this changed to dialling in the international format 00 44, and the 03 range was withdrawn from use.

Director systems in the US

In the United States, most large cities did not use step-by-step equipment, but Los Angeles was a major exception. Before the advent of electronic switching, directors were commonly used in areas of the city served by GTE.