Telephones, their construction and fitting; a practical treatise on the fitting-up and maintenance of telephones and the auxiliary apparatus (1892)
Allsop, Frederick Charles · London, New York, E. & F.N. Spon · leaf 212
nd 3 run directly through the switch, and respectiveindicator drops and bell to earth. If a call is received (letus suppose from instrument No. 3), then person at No. 4instrument moves the lever of his switch to No. 3 point, whichtransfers No. 3 line from the indicator to No. 1 instrument.No. 1 can… … SWITCHBBflRD \BnfiTHy ST/IT/0/V_ A-^-f (r?n-Ei
Telephone
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