Telephone, Hand, A

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Telephone, Hand, A
Instruction in Army Telegraphy and Telephony Volume I - Instruments, 1914 - Chapter 11 Figure 8 (detail).jpg
Telephone, Hand, A, Mark I
Telephone, Hand, A Mark I is intended for use with office telephone sets. Telephone, Portable, A, Switch-boards telephone exchange and with Transmitter, vibrating, Mark IV.[1]

The instrument is of Messrs. Ericsson's design. The receiver is and the coils are wound with •004-inch wire to a resistance of 135 ohms. The switch is a simple contact maker for the microphone circuit, and the flexible cord has four conductors, two for the receiver and two for the transmitter. The cord is known as Cord, telephone, A, is 4 feet long, and quadruple.

Telephone, Hand, A Mark II is generally similar to Telephone, Mark I, and is used for the same purposes. The alterations are intended to make it more durable, and are as follows : —

(a) The receiver leads are entirely enclosed in the case instead of coming through the handle and being attached to terminals outside the receiver.
(b) The ear-piece comprises a threaded metal collar with a removable ebonite disc, instead of being wholly of ebonite screwed direct to the body of the receiver.
(c) The transmitter is of the capsule type.

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References

  1. ↑ Description from Instruction in Army Telegraphy and Telephony Volume I - Instruments, 1914