The telephone system of the British post office. A practical handbook (1901)
Herbert, Thomas Ernest · London, New York, Whittaker and Co. · leaf 96
cords which, when thrown forward,puts the operators speaking set across the cords at the point indicated Compute Operating Connections. 8i in Figure 68. The general form of the key consists of six springs andfour studs; in fact, is very similar to two ringing keys placed side by side,but operated… … Figure 6g. and back of the key respectively. Similarly upon the right, two springsrest upon contact studs, but in this case two springs are placed outsidethese, so that when the ebonite block descends the studs are left discon-nected, and the in^er spnngs make contact with the outer. This is the…
Telephone · Postal service
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