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
Object Name
telegraph receiver
telegraph sounder
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
See more items in
Work and Industry: Electricity
Telegraph Sounders
Data Source
National Museum of American History, Kenneth E. Behring Center


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