main-line telegraph 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.
“Main line” relays like this unit made/used by [name] were one of the most common types of relay and were typically made with a resistance of 150 ohms. As the name suggests, main line relays served on major intercity circuits several hundred miles long. This relay has a 170 ohms rating, somewhat higher than usual.
Location
Currently not on view
Physical Description
brass (overall material)
wood (overall material)
steel (overall material)
plastic (overall material)
Measurements
overall: 3 3/4 in x 9 in x 4 1/4 in; 9.525 cm x 22.86 cm x 10.795 cm
ID Number
EM.331766
catalog number
331766
accession number
294351
collector/donor number
100-014
Credit Line
from Western Union Corporation
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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