![](https://coimages.sciencemuseumgroup.org.uk/50/800/medium_thumbnail_1970_0056__0002_.jpg)
Double-current telegraph key, 1830-1900
- Made:
- 1830-1900 in United Kingdom
- maker:
- General Post Office
![Double-current telegraph key](https://coimages.sciencemuseumgroup.org.uk/43/995/small_thumbnail_1953_0111__0002_.jpg)
![Double-current telegraph key](https://coimages.sciencemuseumgroup.org.uk/43/994/small_thumbnail_1953_0111__0001_.jpg)
![Double-current telegraph key](https://coimages.sciencemuseumgroup.org.uk/43/996/small_thumbnail_1953_0111__0003_.jpg)
![Double-current telegraph key](https://coimages.sciencemuseumgroup.org.uk/43/997/small_thumbnail_1953_0111__0004_.jpg)
Double-current telegraph key, probably made and used by the Post Office, British, 1830-1900.
With a single-current telegraph key the position of the relay is restored to the normal position when current ceases by a magnetic bias or by a spring in tension. In other words, signal currents only flow in the line when the key is depressed. In the double-current system a current in the reverse direction is used to restore the relay to the spacing side. This example is similar to those used with the Bright's bell, or acoustic telegraph.
Details
- Category:
- Telecommunications
- Object Number:
- 1953-111
- Materials:
- wood (unidentified), metal (unknown), copper (alloy) and mother-of-pearl
- Measurements:
-
overall: 60 mm x 130 mm x 230 mm, .86 kg
- type:
- telegraph
- credit:
- Donated by the Institution of Electrical Engineers