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Gray telegraph relay 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 lineGray telegraph relay patent model. 1867. Gray, Elisha. National Museum of American History. CC0.
