telegraph relay

Description (Brief)
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.
This duplex relay was made by Charles Williams, Jr. of Boston and used in experiments by Moses Farmer. Duplex relays operated in a system designed to send two messages simultaneously over the same wire. Williams had made duplex devices for Joseph Stearns who devised the first practical duplex system in 1868 and also made early telephone devices for Alexander Graham Bell.
Currently not on view
Object Name
relay, relegraph, duplex
telegraph key or relay
telegraph relay
date made
ca 1876
Charles Williams, Jr.
Physical Description
brass (overall material)
wood (overall material)
plastic (overall material)
ivory? (overall material)
overall: 4 1/2 in x 6 1/2 in x 7 3/4 in; 11.43 cm x 16.51 cm x 19.685 cm
ID Number
catalog number
accession number
Telegraph Relays & Repeaters
See more items in
Work and Industry: Electricity
Telegraph Relays & Repeaters
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
from Sarah J. Farmer
Additional Media

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