The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 171
158.—Full size lever are similar to those of the 2-coil drop, so that Fig. 157serves as elevation of both kinds. As the magnetic circuitis of very small reluctance the drop is very sensitive, and hasgreat impedance, for which reason it must always be insertedas a shunt to a speaking circuit, and… … Fig. 159.—Scale % currents. Another purpose which the iron jacket serves isto confine the magnetic hues of force to the inside of the coil, SWITCH-BOARD APPARATUS 147 and so prevent inductive effects on adjacent coils. The coilconnections are brought to the outside by straight, stiff wires,which…
Telephone
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