SIEMENS BROTHERS
S51

The S51 System

The S51 used a pre-2000 type switch but with an updated operating system. All the relays were 3000 or 600 type. The Uniselectors were of the PO No. 2 type, but all with a retained but modernised pre-2000 switch mechanism and bank arrangement.

It was thought that this system was preferred in some countries as it was considered easy to maintain.

BR Southern Region had two of these switches, thought by some to have been cheap reject export orders.  This is strange as the PABX No. 3 was at the time being installed elsewhere.

Notes
BR SR installed a S51 at Ashford (300 line) in 1958 and Waterloo (c 1000 lines) in 1964.

Last revised: October 08, 2025

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