Telegraph Sounder

Telegraph Sounder

Usage conditions apply
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. The type 1-B sounder was a very common model for main line use. This unit was rated at 400 ohms resistance and was repaired in Western Union's New York Repair Shop, seen by the stamp on the bottom of the unit.
Currently not on view
Object Name
telegraph receiver
telegraph sounder
J. H. Bunnell & Co.
Physical Description
wood (overall material)
brass (overall material)
rubber (overall material)
overall: 3 3/4 in x 3 in x 5 1/2 in; 9.525 cm x 7.62 cm x 13.97 cm
ID Number
model number
accession number
catalog number
Credit Line
from Western Union Corporation
See more items in
Work and Industry: Electricity
Telegraph Sounders
Data Source
National Museum of American History
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If you connect 100 volts to your 1-b sounder say bye bye to you sounder. They use 6 or 12 volts depending on wiring, series vs parallel.
I may have already said this and if I have I apologize for the duplicate message. All of the Western Union Type 1 Sounders including the 1B were designed for use on the local voltage of telegraph office local loops. The 1B could be wired for either the 100 volt or 30 volt local power busbars available in central offices with hundreds of lines and the multi line offices found in larger cities and towns. 400 OHM wiring was used for 100 volt local loop use to allow a current flow of 250 milliamperes. The 100 OHM connection would be used for 30 Volt local office loops using a current flow of 300 milliamperes. Notice the current flow's similarity to the 1A sounder which has a coil resistance of 4 OHMs and is operated from 1 or 2 cells of gravity battery providing around 1 volt. A current flow of .25 amperes was seldom available on single wire ground return telegraph main lines. Because of the amount of current leakage on outside telegraph lines voltages of 100 volts or more were used to keep ~50 milliamperes flowing in the line. Main line sounders would have coil resistances of 100 Ohms or more but were designed to operate at those lower current flows of less than a tenth of an ampere.
According to the Western Union document Specifications For The Theory and Operation of Single Morse Circuits The Western Union Telegraph Company Engineering Department ©1928 the 1B sounder is listed as used for a local sounder. It was used as the local sounder in large switching and repeater offices where the local loop voltage was 12, 24, or 48 volts. This sounder was designed to take advantage of the large supply of higher voltage current at such offices.

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