The telephone system of the British post office. A practical handbook (1901)
Herbert, Thomas Ernest · London, New York, Whittaker and Co. · leaf 177
ed for the whole ten pairs of pegsand speaking keys, and thus it becomes necessary to put these ringingkeys in with the operators telephone—i.e., the speaking keys switch theparticular pair of cords through the ringing keys to the operatorstelephone. In order to accomplish this, a speaking or, as… … :^ Ti*«(SMiTT6a. Figure 130. The complete connections of a pair of cords, speaking key, and theoperating connections are shewn in Figure 130. The five springs of thespeaking key are furnished with four contact stops, upon which they restwhen in the speaking position shewn. In order that we may ring…
Telephone · Postal service
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