The telephone system of the British post office. A practical handbook (1901)
Herbert, Thomas Ernest · London, New York, Whittaker and Co. · leaf 53
e receiver is liftedoff, the steel spring causes the lever to rise, making contact with the bottomstop, and thus joining up the receiver and secondary coil. The two springsnow rest on the insulated metal plate, and are thus connected, completingthe microphone circuit. It was soon discovered that… … TO MICROPHONE TO SBZONDAR* 8t R£CCtVEPS TO l^ienOPHONB Figure 29. In the Post Office form of the instrument the two circuits are keptdistinct, two springs being provided. The switch-arm (Figure 29) consists Switch-Anns. 39 of a brass lever, the end of which is in the form of a circular rod. Thetwo…
Telephone · Postal service
Internet Archive · Cornell University Library · Public Domain Mark 1.0. Free to use for anything.
