Hall duplex telegraph relay


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 Thomas Hall 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. Someone, Farmer himself perhaps, removed the electromagnet coils prior to the donation of the relay in 1899.

Date Made: ca 1875

Maker: Farmer, Moses G.Hall, Thomas

Location: Currently not on view

See more items in: Work and Industry: Electricity, Communications, Telegraph Relays & Repeaters


Exhibition Location:

Credit Line: from Sarah J. Farmer

Data Source: National Museum of American History

Id Number: EM.181947Catalog Number: 181947Accession Number: 2015.0173

Object Name: relaytelegraph relay

Physical Description: wood (overall material)brass (overall material)steel (overall material)Measurements: overall: 4 in x 9 3/4 in x 5 3/4 in; 10.16 cm x 24.765 cm x 14.605 cm

Guid: http://n2t.net/ark:/65665/ng49ca746a5-407e-704b-e053-15f76fa0b4fa

Record Id: nmah_706631

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