On Mar 29, 10:19 am, wrote:
"MarkVarley - MVP" wrote in messagenews:1i3su3l4mnujt4fomcdclu3mvanq5rpum4@4ax .com...

I've seen notices that imply this, perhaps the train knows when it's
physically in a station and is automatic until it leaves.

Perhaps that is the case as some models of trains have a pretty fast pick up
and perhaps the driver won't be able to react quickly enough to an alarm if
part of the train is still in the station.

I'm sure that it's quite easy for a train to tell if it is still in the
platform.

Blimey, how high tech do you think the tube is! :-)

There are count up markers showing how far the train is out when it is
leaving a station. If a Passenger Emergency Alarm is activated whilst
within the last one then the train must stop and the PEA should be
investigated.
If activated between stations outside of the count up markers, then it
should continue to the next station, where it will be investigated.
On some line; Metropolitan and Circle and District are three, the
operation of the PEA will apply the brakes and operate audible and
visual warnings in the cab. Once they have been released, a Brake
Overide Device, a foot plunger can be operated so that the train can
continue to the next station.
On some line, I believe the Jubilee to be one, the train brake will
not apply if the alarm is acknowledged, and then some lines have the
benefit of knowing what car the alarm has been operated in, so station
staff can get to the operated alarm quicker, plus some also have a
talkback so the train operator can talk with the person who has
operated, to gleam further information.