| UAX Introduction.
A UAX (sometimes abbreavated to U followed by the type number) is a Strowger type automatic telephone exchange. These Unit Automatic eXchanges were developed by British Telephone Equipment Manufacturers in conjunction with the British GPO. They were developed to allow the replacement of manual exchanges in rural areas. These manual exchanges were limited in the services that they could offer, most of them being in the front room of the operators house, and were quite often only manned during the day. They often had to be moved quickly when the operator ceased working for the GPO, or if the operator got ill. The idea of replacement with a 'robot' or automatic exchange would allow a constant level of service to be maintained at all times, and would be located in its own building so that once it had been installed, that was it, until it was too small to cope any more.
These exchanges were designed on a unit basis (hence the name) so that the minimum outlay would be required to get the exchange working. Most early UAXs started with the capacity for 25 subscribers, and when this maximum was almost reached, the next unit would be added, so allowing the cost of the whole exchange to be staggered over a period of time.