Manhattan Electric pony telegraph relay

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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 Manhattan Electric Supply Co., serviced private lines and shorter branch circuits. The resistance of a given pony relay varied depending on the length of the circuit. This 10 ohm pony relay would have been used on circuits up to about 7 miles in length.
Currently not on view
Manhattan Electric Supply Co.
Physical Description
wood (overall material)
metal (overall material)
brass (overall material)
cloth (overall material)
overall: 3 in x 6 1/2 in x 3 1/2 in; 7.62 cm x 16.51 cm x 8.89 cm
ID Number
collector/donor number
accession number
catalog number
Credit Line
from Oberlin College, Dept. of Physics, thru David L. Anderson
See more items in
Work and Industry: Electricity
Telegraph Relays & Repeaters
Data Source
National Museum of American History


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