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 218
Connections for adding an Extension Bell. what is called an extension bell, instead of the third instru-ment. This enables the bell to be placed at such a place whereit might not be convenient to fix the telephone, so that thesignals can be better heard. It is convenient also where the r-±i_i … STfilTION N92. J
Telephone
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