Pony-type 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 used by Charles Heaton 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 about 7 miles in length. Heaton used this relay in the South Bend, Indiana office of the Erie & Michigan Telegraph Line when he opened the office in 1848 and kept it in service until 1872.
Currently not on view
date made
Heaton, Jr., Charles M.
Physical Description
wood (overall material)
brass (overall material)
silk (overall material)
ivory (overall material)
steel (overall material)
overall: 9 in x 5 5/8 in x 5 3/4 in; 22.86 cm x 14.2875 cm x 14.605 cm
ID Number
catalog number
accession number
Credit Line
from Telegraph Historical Society, thru Charles M. Heaton
See more items in
Work and Industry: Electricity
Telegraph Relays & Repeaters
Data Source
National Museum of American History


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