Telephone Exchange Names - Europe

Europe

Two of the most notable cities using the first three letters, four digits system, known as 3L-4N, with the 3L digits comprising the first three letters of the (local) exchange name were Paris and London. They are examples of the “big-city” problem, with a large city served by many manual exchanges, which could only be converted to automatic gradually, and necessitating operation with a mixture of manual and automatic exchanges for some years.

Telephone directories showed the first three letters of the exchange in bold caps if all seven digits were to be dialled; for example, a subscriber's number on London's Whitehall exchange was shown thus: "WHItehall 1212" (the number of Scotland Yard).

If the first three letters were in capitals but not bold capitals, eg HAYes 1295, the caller would dial the first three digits (the ABC digits) only, and when connected to Hayes ask the Hayes local operator for the local number (here 1295). Later call indicator working equipment was installed at some manual exchanges so that the caller could dial all seven digits, and the required number would be displayed to the local operator.

In the United Kingdom, the first Director exchange in London, Holburn Tandem, was cutover in 1927; preceded by any necessary changes in the London area, eg changing some exchange names and making all local numbers (4N) 4-digit. As each digit represents three letters the same network cannot have exchanges called BRIxton and CRIcklewood, which both correspond to 274. In smaller director areas some A-digit levels were combined so that local director exchange would only need four or less groups of directors instead of eight. But if (say) A-digit levels 7 and 8 were combined it would not be possible to have both PERivale and TERminus exchanges in the same network.

The other main UK conurbations followed suit, namely Manchester in 1930 (e.g., DEAnsgate 3414, the number for Kendals department store), Birmingham (in 1931), Glasgow (in 1937), and later Liverpool and Edinburgh (c1950).

The standards for converting exchange name letters in Europe varied, notably in the placement of the letters O, Q and Z.

The switchover to all figure dialling began in the UK in 1966 following the successful conversion of telephone numbers in Paris, in 1963, which until then had also used the 3L-4N combinations. For example, POMpadour became 706, LOUvre was 508, and PIGalle was replaced by 744.