Telegraph Sounder and Speaking Telephone
From the collection of National Museum of American History. Free to download, adapt and use — no permission needed.
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. Inventor Amos Dolbear, known for his early experiments in telephony, made this patent model of a combination device that worked both as a telegraph sounder and a telephone receiver.
National Museum of American History’s own description
