Bletchleyite
Veteran Member
The red one is the passcomm. The green one is the call for aid.
If operated when departing from a station the red one will apply the brakes immediately. The driver cannot override this when departing from a station, so if you see something that is immediately life threatening such as a trap and drag incident, break the cover and hit the red button straight away. For anything that isn't immediately life threatening use the green one and the driver or guard will respond as soon as it is safe to do so.
Indeed, that's the German model and it makes a LOT of sense - most things don't require the train to stop (given that it's not DOO), but those things that do require it to stop tend to require it to stop NOW, not after a short discussion.
ISTR that all Eurostars (and probably TGVs by extension) have this setup as well. It may well I suppose be that Northern didn't specify anything other than its existence, so it just got what Spain fitted as standard.