Telegraph Sounder

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, portable telegraph unit was known as a "secret sounder" and could be attached quickly to a telegraph line for military use or for tests by maintenance crews. Containing both a key and a sounder in a closed box, the unit is associated with US Patent #760029, issued to John F. Skirrow on 17 May 1904. The patent does not specifically mention a secret sounder but explains a method of adjusting the position of the electromagnets in a sounder (or "other forms of electric signaling instruments") without affecting the angle between the armature and magnet cores. Skirrow also claimed that his innovation resulted in a simpler way of adjusting sounders.
Currently not on view
date made
ca 1905
Skirrow, John F.
Physical Description
brass (overall material)
wood (overall material)
steel (overall material)
closed: 1 3/4 in x 6 1/2 in x 4 1/2 in; 4.445 cm x 16.51 cm x 11.43 cm
open: 2 1/4 in x 6 1/2 in x 4 1/2 in; 5.715 cm x 16.51 cm x 11.43 cm
ID Number
patent number
collector/donor 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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