G.P.O. Clock No. 38 - for synchronising 30 second pulse clocks

This clock was used to time calls in trunk exchanges. It was also used to check the accuracy of the (smaller) Master Clock No.46, which did not have a facility to drive the normal 30 second slave dials.
More information on all G.P.O. clocks can be found at:http://gpoclocksystems.byethost22.com