4 ms·
IIRC the analogy is to the positions of a stop/go safety flag (or an actual railway semaphore https://en.wikipedia.org/wiki/Railway_semaphore_signal https://en.
by leoc 12y ago
IIRC the analogy is to the positions of a stop/go safety flag (or an actual railway semaphore https://en.wikipedia.org/wiki/Railway_semaphore_signal https://en.wikipedia.org/wiki/Railway_semaphore_signal !) meant to ensure that only one train is in a railway tunnel at a time. A Dutch-speaker with EWD35 http://www.cs.utexas.edu/users/EWD/ewd00xx/EWD35.PDF http://www.cs.utexas.edu/users/EWD/ewd00xx/EWD35.PDF should be able to confirm this.
- theoh 12y agoI think that much is clear, (the railway analogy), but the idea that tunnels are the main use case for semaphore signals is daft. All railways use variations on the principle of block signalling, where only one train is allowed on any section of track, even if successive trains are travelling in the same direction. This ensures safe separation of trains, which take some distance to stop.