Western Electric pony telegraph relay

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Description
Telegraph relays amplified electrical signals in a telegraph line. Telegraph messages traveled as a series of electrical pulses through a wire from a transmitter to a receiver. Short pulses made a dot, slightly longer pulses a dash. The pulses faded in strength as they traveled through the wire, to the point where the incoming signal was too weak to directly operate a receiving sounder or register. A relay detected a weak signal and used a battery to strengthen the signal so that the receiver would operate.
So-called “pony” relays like this unit made by Western Electric serviced private lines and shorter branch circuits. The resistance of a given pony relay varied depending on the length of the circuit. This 100 ohm pony relay would have been used on circuits up to about 100 miles in length.
Location
Currently not on view
date made
ca 1905
maker
Western Electric
Physical Description
slate (overall material)
iron (overall material)
brass (overall material)
rubber (overall material)
Measurements
overall: 3 1/2 in x 7 in x 4 in; 8.89 cm x 17.78 cm x 10.16 cm
ID Number
EM.322148
catalog number
322148
accession number
244197
Credit Line
from the Massachusetts Institute of Technology, Dept. of Electrical Engineering, thru John A. Tucker
See more items in
Work and Industry: Electricity
Communications
Telegraph Relays & Repeaters
Data Source
National Museum of American History, Kenneth E. Behring Center

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