Gray telegraph relay patent model

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.

This relay was constructed early in 1867 by noted electrical inventor Elisha Gray to accompany a patent application. He received US Patent 69,424 later that year for an improved telegraph relay. Gray's idea was to use a second set of electromagnet coils rather than a spring to retract the armature after a signal pulse. He wrote that the pulse's strength could vary so much that a relay's spring needed constant adjustment. His design compensated automatically for the variation in pulse strength.

Date Made: 1867

Maker: Gray, Elisha

Location: Currently not on view

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

Exhibition:

Exhibition Location:

Data Source: National Museum of American History

Id Number: EM.308870Catalog Number: 308870Accession Number: 89797Patent Number: 69424

Object Name: relaytelegraph relayObject Type: Patent Model

Physical Description: wood (overall material)brass (overall material)plastic (overall material)cloth (overall material)Measurements: overall: 4 1/2 in x 11 1/2 in x 5 3/8 in; 11.43 cm x 29.21 cm x 13.6525 cm

Guid: http://n2t.net/ark:/65665/ng49ca746ab-8a01-704b-e053-15f76fa0b4fa

Record Id: nmah_706268

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