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. The type 1-B sounder was a very common model for main line use. This unit was dual rated for both 18 and 400 ohms resistance so it could be used on both local and main line circuits.
Location
Currently not on view
Object Name
telegraph receiver
telegraph sounder
maker
J. H. Bunnell & Co.
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.331513
accession number
294351
catalog number
331513
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

I believe that what has been read as 18 on the label is actually 1B. 2 200 Ohm resistances in Series are 400 Ohms because resistances in series add to the total resistance of that circuit. When equal resistances are connected in Parallel the resistance of a single resistance is divided by the number of resistances. In this case you have 2 200 Ohm resistances in Parallel 200/2 = 100 Ohms.

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