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. This particular sounder is mounted on a display plate from the Western Union Museum and gives a manufacturing date of 1928.
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