Pattern No. B630
Comprises Granular Carbon Transmitter, Watch Receiver, Cord, Automatic Switch-hook, Induction Coil, Two Magnet Generator, Bell, Line Selector, and Second Lever to cut the other lines off the circuit.
These instruments are intended for use where the stations between which intercommunication takes place are too far apart for Battery Ringing Sets further, they are cheaper to maintain than the latter. Pattern No. B625 is fitted with a mechanical click, which reduces the risk of making contact with two stations at once. Pattern No. B630, having a means of cutting the other lines off the circuit, allows of more privacy during conversation.
5, 10, 15, 20, 25 & 30 line models.