Greeley main-line telegraph relay

Greeley main-line telegraph relay

<< >>
Usage conditions apply
Downloads
Description
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.
“Main line” relays like this unit were common. Typically made with a resistance of 150 ohms, main line relays served on major intercity circuits. According to George C. Maynard, the curator who collected this piece in 1891, "This specimen seems to be a very slightly modified version of the Western Union Relay No. 2 of the Tillotson Company which was introduced in a 150 Ohms model about 1880-1881 at $8.50. As late as 1893 the E. S. Greeley Co. was still using the Tillotson illustration of 1880-1881. However the caption had been changed to 'Improved Western Union Relay'.... The armature or lever in this model is the old style of two-piece construction. A bar across the poles of the magnet is attached to the lever [instead of a single-piece lever]."
Location
Currently not on view
Object Name
telegraph relay
date made
1891
maker
E. S. Greeley & Company
Physical Description
wood (overall material)
brass (overall material)
steel (overall material)
plastic (overall material)
Measurements
overall: 3 1/2 in x 8 3/4 in x 4 1/2 in; 8.89 cm x 22.225 cm x 11.43 cm
ID Number
EM.181117
accession number
25412
catalog number
181117
Credit Line
from the E. S. Greeley Co.
See more items in
Work and Industry: Electricity
Communications
Telegraph Relays & Repeaters
Data Source
National Museum of American History
Nominate this object for photography.   

Our collection database is a work in progress. We may update this record based on further research and review. Learn more about our approach to sharing our collection online.

If you would like to know how you can use content on this page, see the Smithsonian's Terms of Use. If you need to request an image for publication or other use, please visit Rights and Reproductions.

Comments

Add a comment about this object