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.
This pole-changing relay includes a plate citing "F. W. Jones Patents / April 17, 1888 / April 29, 1890." The citation refers to US Patents 381,251 and 426,819, respectively. Francis W. Jones of New York City received these patents for his inventions related to improvements in operating duplex and quadruplex telegraph devices on "dynamo machines" rather than primary batteries.
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