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Williams-Farmer duplex telegraph patent model
From the collection of National Museum of American History. Free to download, adapt and use — no permission needed.
About this work
Telegraph relays amplified electrical signals in a telegraph line. Telegraph messages traveled as a series of electrical pulses through a wire from a transmitter to a receiver. Short pulses made a dot, slightly longer pulses a dash. The pulses faded in strength as they traveled through the wire, to the point where the incoming signal was too weak to directly operate a receiving sounder or register. A relay detected a weak signal and used a battery to strengthen the signal so that the receiver would operate.
National Museum of American History’s own descriptionCredit lineWilliams-Farmer duplex telegraph patent model. 1875. Farmer, Moses G.. National Museum of American History. CC0.
