The telephone system of the British post office. A practical handbook (1901)
Herbert, Thomas Ernest · London, New York, Whittaker and Co. · leaf 141
drop. The only point which now remains to be dealt with is in reference tothe automatic ring-off given when the caller rises from the seat. This isaccomplished by the speaking battery and a non-polarised drop indi-cator at the counter. The B line of the pair of wires between thecounter and the… … Figure 105. passes through the contacts of the cabinet seat to the counter, and thencethrough the non-polarised indicator in connection with the cabinet on tothe top spring of the eight-point switch-spring. The central spring ofthis switch-spring is connected to the B line of the circuit to the…
Telephone · Postal service
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