Telegraph Test Unit

Description (Brief)
Telegraph sounders convert electrical pulses into audible sounds and are used to receive Morse code messages. The message travels as a series of electrical pulses through a wire. Short pulses make a dot, slightly longer pulses make a dash. The sequence of dots and dashes represent letters and numbers. The pulses energize the sounder’s electromagnets which move a lever-arm. The arm makes a loud “click” when it strikes a crossbar and the operator translates the pattern of sounds into the original language. This small, pocket-sized unit was both transmitter and receiver. It has a leather case and was used by Western Union personnel in the field for testing telegraph lines.
Currently not on view
Physical Description
leather (overall material)
metal (overall material)
plastic (overall material)
overall: 2 3/8 in x 5 3/4 in x 2 7/8 in; 6.0325 cm x 14.605 cm x 7.3025 cm
ID Number
accession number
catalog number
collector/donor number
Credit Line
from Western Union Corporation
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Work and Industry: Electricity
Telegraph Sounders
Data Source
National Museum of American History


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