AUTO is short for automatic.  Almon Strowger, an undertaker from Kansas (USA), invented a basic electromechanical exchange for automatically switching telephone calls.  He did this because he thought that his rivals wife, who worked on the towns manual telephone exchange, was diverting his calls to her husband.  Strowgers system automatically routed calls without the assistance of an operator.  The telephone instrument has to have a dial and his system known as `Strowger' was still used in UK public exchanges until a few years ago.

Strowger systems are not the only type of automatic exchange in existence.  Many others were made based on a variety of components ranging from relays to wafer switches.

The BPO introduced Crossbar and Electronic exchanges in the late 1960's - early 1970's and these were superseded by System X and System Y (both digital).

These and other public exchange systems are too complex a subject to describe in this document and you are advised to read Telephony by Atkinson, or browse to an exchange related web site, for a complete technical description.

History of the Automatic Telephone System

Try the visit to a PABX 3 page - it's all Strowger, although only a customer system.


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Last revised: January 22, 2020