Connection and Operation of the Line
المؤلف:
GEORGE A. HOADLEY
المصدر:
ESSENTIALS OF PHYSICS
الجزء والصفحة:
P-372
2025-12-10
5
Let Fig. 1 represent, diagrammatically, a line having Philadelphia and New York for its terminal stations and Trenton for an intermediate station. The connections are arranged for sending a message from New York to Philadelphia. The switch S at Philadelphia is closed, that at New York is open.
When the operator at New York presses his key, the connection is made along the line, and the relay at Philadelphia is magnetized. The armature A is attracted, moves toward the magnet, and comes in contact with the pin P; and as this is coupled to one side of the local battery and the armature to the other side through the sounder, the local circuit is made and the sounder attracts its armature. As soon as the sender at New York releases his key, the circuit is broken, A is pulled back to its normal position by a spring, the local circuit is broken, and the condition is just as it was before the signal was sent.
The message sent to Philadelphia may also be read at Trenton; for the current has the same effect on any intermediate relays that it has on the Philadelphia relay. If the message had been intended for Trenton, the New York operator would have first sent the Trenton "call" until the Trenton operator had responded, showing that he would pay attention.
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