Manhattan Electric pony telegraph relay

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 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 20 ohm pony relay would have been used on circuits up to about 15 miles in length. This instrument was used at the American Telegrapher's Tournament Association contest in Philadelphia, on October 30 and 31, 1903. The equipment was donated to the Smithsonian Institution afterwards.
Location
Currently not on view
date made
1903
maker
Manhattan Electric Supply Co.
Physical Description
steel (overall material)
iron (overall material)
plastic (overall material)
brass (overall material)
wood (overall material)
paper (overall material)
Measurements
overall: 3 in x 6 3/4 in x 3 1/2 in; 7.62 cm x 17.145 cm x 8.89 cm
ID Number
EM.222129
catalog number
222129
accession number
41948
Credit Line
from Manhattan Electric Supply Co. thru Clarence A. Stimson
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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