"David Walters" wrote in message
...
What is it about the Northern line train radios not working that
stops the usual service pattern (particularly trains from both
Edgware and High Barnet taking both central branches) from running?

Part of the job of the train radio is to carry the train radio alarm traffic
that notifies the Line Controller in the event that a train becomes stalled
in a tunnel due to an incapacitated Train Operator (due to EG heart attack)
I'm not familiar with the Northern stock, but on the Picc. if the deadman is
released for 60 seconds an alarm starts to sound in the cab. Should the
driver not respond to this alarm in the following 30 seconds the OPO alarm
is operated, this sends a radio signal to the Controller and illuminated the
"calling on" light on the rear of the train. Should this happen, the
equipment allows the Controller to open up the trains PA to inform
passengers (and possibly ask for any member of staff travelling on the train
to go to the front cab and find out what's going on). The radio is also
required to contact the train behind and get that Operator to trip his train
forward and instigate the "stepping through" procedure. All of this was
required as part of the railway safety case that LUL had to present to HMRI
to get them to allow the introduction of OPO train operation on deep level
tube lines, previously all of these functions would have been performed by
the Guard.
HTH
--
Cheers, Steve.
Change from jealous to sad to reply.