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.
This small, portable telegraph unit was known (probably generically) 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
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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From the research I have done that is not a secret sounder. The term secret sounder was applied to sounders which only the user could hear. One form of secret sounder was so small that it fit inside of a housing no bigger than an older headset earphone. the telegrapher would wear it on a metal band over the top of their head positioned over 1 ear. Actual use was often not for secrecy but to allow a telegrapher to receive in a noisy environment such as the press box of a sporting event. Ronald Reagan used one of this type in broadcasting Baseball games. As Reagan was working in the broadcast both of the radio station he had to be able to receive the play by play from a reporter located at the stadium in the press box. The Secret Sounder was used so that the telegraph signal would not be heard on the broadcast via the sound booth's microphone. I believe that this item in the collection was simply a portable Sounder with key suitable for use on poles by the line maintainers. The far smaller pocket sets were used by spies and uniformed telegraph scouts from cavalry or mounted light infantry units. The pocket sets were designed for maintainers but they were so compact that they worked quite nicely for clandestine use. The Confederate Army announced that anyone found with a pocket set without identification as a signal maintainer employed in the immediate area would be immediately hung. Because Telegraph Scouts were uniformed soldiers US General George Meade announced that for every telegraph scout hung a confederate prisoner chosen by lot would also be hung. The Confederacy clarified that the warning applied only to those found with a pocket set while in civilian clothing. Here is a link to the W1TP virtual Telegraph museum. Tom Perara's descriptions of various telegraph apparatus is considered authoritative among telegraph instrument collectors. I'm only suggesting that the responsible curator reexamine the use of the phrase "Secret Sounder" in the description of that repairers telegraph set. -- Tom Horne 240-688-8590
Hi Tom: Many thanks for your thoughtful and detailed comment! I've modified the entry to indicate that the term secret sounder was probably being used generically. I expect that you're correct as to the specifics of this object. I checked and it is identified in the Western Union Museum catalog as a secret sounder, as are several other units that appear quite different. That would seem to indicate that the term had become generic for these small telegraph sets at some point, at least within that museum or possibly within the company itself. Object details in the WU Catalog vary as to content and completeness. The WU Museum closed around 1970, so we may never know for certain. My predecessor worked to rescue their holdings and brought the entire collection to the Smithsonian in 1972. One example is EM.331984 - a pocket watch type telegraph set. We also have a framed advertisement to accompany that object. The ad (linked to the online record) refers to it as a Secret Sounder. EM.332271 and EM.332773 appear to be of the headset type you mention. Both are also identified in the WU Catalog as secret sounders. EM.331949 may be the container for one of these headsets. The sheet inside the lid reads: "Instructions for the operation of secret sounders." We also have two line test sets, and four "pocket telegraph" sets in the collection. Our first Electricity curator, George C. Maynard, was a Civil War veteran and a telegrapher by training, and collected EM.232582 in 1904. It's one of the two line test sets and he identified it as a pocket telegraph, though it doesn't have the enclosure seen on the others. EM.181773, a presentation unit given to Samuel Morse, is an example of those. So I suspect that term may have passed into generic use as well. Thanks again for the comment! Maybe the WU Museum's identification is simply an error or maybe it indeed represents a generic use of a specific term. Either way, it raises the interesting question about how technical language morphs over time. Hal Wallace, Curator, NMAH Electricity Collections

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