tripcocks

Noun

tripcock (plural tripcocks)

1. A train-mounted safety device which interacts with a trackside device to stop a train automatically if it passes a signal at danger (showing a red light).
   • When a train runs onto the track, thus connecting the two rails, a short circuit is created, the current drops out and the signal switched to red. The system operates in conjunction with a lever on the tracks. If a train should pass a red light, the lever, which is called a tripcock, comes into...2012, Andrew Martin, Underground Overground: A passenger's history of the Tube, Profile Books, →ISBN, pages 136–137