Introduction
At the time of writing this blog post, the standard length for telephone numbers in the UK (be they mobile, landline or special numbers) is 11 digits in the standard national format (12 digits when shown in international format with the country code of 44 added and the leading 0 of the dialing code removed).
UK Telephone numbers have not always been this length though, the length of numbers has increased as the demand for additional numbers has increased, due to innovations such as fax machines, mobile phones and even direct dialling of business numbers. In this blog post, I am going to take a short look at how the telephone numbers have evolved over time.
In the beginning
When telephones were originally introduced, the concept of direct dialing did not exist and calls were placed through the operator. During this time telephone numbers were usually quoted as the Exchange Name, followed by the subscriber number (the unique number of the individual/organisation), such as Whitehall 1212, which was the telephone number for Scotland Yard.
With this manual system, the caller would connect to the operator and simply ask to be connected to “Whitehall 1212” and the operator would connect them.
During this period, the length of individual telephone numbers depended on the number of subscribers attached to a particular exchange. A small exchange with fewer than 10 subscribers, would only need a single digit subscriber number, but an exchange with thousands of lines would require four or even five-digit subscriber numbers.
As demand for telephones grew, more telephone numbers were required. This would often see an exchange with existing two-digit numbers open one or more new ranges with three-digit local numbers. This piecemeal approach lasted until the 1980s when an overhaul of dialling codes and subscriber numbers took place due to increased demand for numbers.
Introduction of the Director system
In the early 1920s, the General Post Office trialled several automatic exchange systems and in November 1922, they decided to adopt the Strowger system, initially for small and medium towns and cities. This would allow callers to directly dial other subscribers within the same exchange area, without the need to place the call via the operator
However, in London, where there were many exchanges covering local areas the development of the Director telephone system was required to enable the operation of both automatic and manual exchanges for several decades while exchanges were automated.
This automation required the ability to be able to identify exchanges numerically, and this was done by assigning letters to each number from 2 to 0 on the telephone dial as follows:
2 – A, B, C
3 – D, E, F
4 – G, H, I
5 – J, K, L
6 – M, N
7 – P, R, S
8 – T, U, V
9 – W, X, Y
0 – O, Q
A three-digit code that was represented by letters was then used to identify the exchange So, taking the example of Whitehall, the exchange was identified by the letters WHI (first three letters of the exchange name), which was represented by the code 944. This means that to dial Scotland Yard, the number would be 944 1212.
In addition to London, the Director system was gradually introduced to other major cities in the UK, such as Birmingham, Edinburgh, Glasgow, Liverpool and Manchester
Rural Automatic Exchanges
Outside of the major cities where Director systems were implemented, standardised automatic exchanges were gradually introduced to smaller towns and rural areas. The RAX were connected to a ‘parent’ exchange in a larger town.
These Rural Automatic Exchanges (RAX) initially only allowed subscribers to call numbers on the same exchange. For calls to other exchanges, subscribers had to dial ’0’ to connect to an operator at a manual switchboard at the parent exchange. Later developments of RAX exchanges introduced direct dialling to parent automatic exchanges by dialling ‘9’ followed by the subscriber number, and direct connections to manual operators at other nearby exchanges by dialling ‘6’, ‘7’ or ‘8’.
From 1925, ‘large multichange exchange areas’ were developed allowing ‘satellite’ exchanges within provincial cities to be connected to a main exchange. These satellite exchanges each used different number ranges without separate dialling codes.
From 1937, the introduction of Unit Automatic Exchanges (UAX) provided local dialling codes for the first time outside the Director areas. This enabled subscribers to directly dial calls to and from nearby automatic exchanges using short dialling codes. However, unlike Director codes or modern dialling codes, the code for a specific destination would vary from exchange to exchange. For example, the local code for Totnes was 997 from Bigbury, but 882 from Blackawton and 86 from Paignton. Long distance (trunk) calls beyond the local call charging area still required connection by an operator, until Subscriber Trunk Dialling (STD) was introduced in 1958, allowing subscribers to dial trunk calls without operator assistance. You can find details of this and the subsequent changes to telephone numbers in the second part of my post on the history of UK telephone numbers.
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