c1966; a close-up of one of the radio consoles used in the Police Control Room at Stoke City Police Headquarters in Hanley. As seen in the photograph, the radio call-sign used in those days was M2YW and operation was via a series of key switches - left to right;
1) Speak (probably a red knob and not latched)
2) Pip Tone (indicating channel busy)
3) Up for test Tone (presumably 1KHz), down for System Talk-Through
4) Normal (standby) and Transmit
On the upper right of the console is a key switch used to disable the warning bell when there was a power failure or power restore.
At the time of placing this photo on the site, I have no information as to why three speakers, each it seems with a corresponding volume control. It suggests either a three channel system, or a three site, single channel system.
Picture Source: Bryn Oliver
Copyright: assumed Crown