Polsey telegraph relay

<< >>
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 relay was made by John Polsey & Company of Boston, a firm better known for making clocks. Polsey (1816-1873) established the firm about 1859 and closed it in 1864. Western Union Company donated the relay to the Smithsonian in 1904 and reported that the relay was "a relic of the Confederacy and was used at Fort Sumter by W. R. Cathcart, manager for many years of their Columbia, SC office who was stationed at that fort as a military operator."
Currently not on view
date made
ca 1862
J. Polsey & Co.
place made
United States: Massachusetts, Boston
Physical Description
marble (overall material)
metal (overall material)
plastic (overall material)
overall: 4 in x 10 1/4 in x 5 1/2 in; 10.16 cm x 26.035 cm x 13.97 cm
ID Number
catalog number
accession number
Credit Line
from Western Union Telegraph Company
See more items in
Work and Industry: Electricity
Telegraph Relays & Repeaters
Data Source
National Museum of American History


Add a comment about this object