The telephone system of the British post office. A practical handbook (1901)
Herbert, Thomas Ernest · London, New York, Whittaker and Co. · leaf 175
FiGUiSE 128. The general appearance of the switch-board and a sectional drawingare shewn in Figujre 128. Each subscribers line terminates upon a switch-spring and an indicator. The switch-springs are acommodated at the top Indicators and Switch-Springs. i6i of the board, and it will be observed…
Telephone · Postal service
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