. The practical telephone handbook and guide to the telephonic exchange . tter a thin Germansilver spring is clamped. When a shutter falls this springis forced into contact with the wire by a small projection,and at night this wire and the frame of the drops form theextremities of a circuit in which is a battery and an electricbell, so that on a shutter falling the circuit is completed, andthe bell rings. A 2-way switch is usually included in thecircuit, so that the circuit may be broken in the 2-coil drops just described have usually a resistance of100 ohms. Tubular or Ironclad D
. The practical telephone handbook and guide to the telephonic exchange . tter a thin Germansilver spring is clamped. When a shutter falls this springis forced into contact with the wire by a small projection,and at night this wire and the frame of the drops form theextremities of a circuit in which is a battery and an electricbell, so that on a shutter falling the circuit is completed, andthe bell rings. A 2-way switch is usually included in thecircuit, so that the circuit may be broken in the 2-coil drops just described have usually a resistance of100 ohms. Tubular or Ironclad Drops.—Fig. 158 shows a 146 PRACTICAL TELEPHONE HANDBOOK form of drop extensively used and designed specially forring-off or clearing drops. It is usually wound to 1000ohms resistance, and it differs from the drop just described inhaving but one long coil, m, which is enclosed in a soft-ironcase or tube, F, made out of the solid metal, the core beingscrewed into this. The armature A is a round disc which, asit were, forms the lid of the case; the shutter and releasing. 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 never directly in thecircuit. This indicator offers great impedance to the rapidlyalternating speaking currents, but only its normal ohmic re-sistance to the comparatively slowly alternating ringing
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Keywords: ., bookcentury1900, bookdecade1900, booksubjecttelephone, bookyear19
