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 sounder was made using US Patent #92284, issued July 6, 1869 to William Davis of Jersey City, NJ. Davis' idea was to make the sounder produce a "clear tone" by using a hollow resonating chamber made of hard rubber. The chamber can be seen mounted on the base next to the electromagnet. The anvil with its adjusting screws is mounted on top of the chamber. When the lever strikes the anvil the resonating chamber amplifies the sound.
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