Telegraph Sounder

Telegraph Sounder

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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 sounder, made by Western Electric, is rated at 50 ohms. Lower resistance units such as this tended to be used on local lines only a few miles in length.
Location
Currently not on view
Object Name
telegraph receiver
telegraph sounder
maker
Western Electric
Physical Description
wood (overall material)
brass (overall material)
rubber (overall material)
Measurements
overall: 3 1/2 in x 5 1/2 in x 3 in; 8.89 cm x 13.97 cm x 7.62 cm
ID Number
EM.331763
accession number
294351
catalog number
331763
collector/donor number
100-015
Credit Line
from Western Union Corporation
See more items in
Work and Industry: Electricity
Communications
Telegraph Sounders
Data Source
National Museum of American History
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Comments

This sounder is a repeating sounder in that it not only makes the clicks needed to read a signal by ear but also functions as a relay by closing a connection between the 2 wire binding post terminals located at the Anvil Frame end of the Sounder's base. Repeating Sounders were most often used as a part of a complete bidirectional Repeater. Repeaters apply main line battery to the section of line that is leaving the repeater station in the opposite direction from the line section that brought that signal pulse to the Repeater station. Repeater stations would be located frequently enough along the telegraph line to maintain the voltage in every section of the line at a high enough value to keep the requisite 40 to 90 Milliamperes of current flow needed to operate the receiving relays or main line sounders of the individual telegraph offices served by each line segment.

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