The telephone system of the British post office. A practical handbook (1901)
Herbert, Thomas Ernest · London, New York, Whittaker and Co. · leaf 103
t angles to thetube is now being tried, with excellent results. The diaphragm keeps theinside of the transmitter dry, and to clean it it is only necessary to removethe mouthpiece. 88 The Telephone System of the British Post Office. CHAPTER XIV. The a Switch Section. Having now examined every part… … Figure 75. is used. Upon an A switch section three pairs of pegs, with theircorresponding three speaking keys, six ringing keys, and ring-oflf indicators,are fitted. The ring-off indicators are placed at the top of the section,the self-restoring indicators being placed uppermost. Beneath the…
Telephone · Postal service
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