Mike Bristow wrote:
In article ,
Fossil wrote:
*Stupid question* Just wondering what they're for, normally one side
has a load of cables going along with two metal wires at the top and
the other has big fat cables.

The two metal wires are the emergancy signal phone (it has a proper
name, which I forget).

It's called the Tunnel Telephone, it has nothing to do with the signalling.

Basically, in the cab of the train is a
telephone headset, which the driver can clip on to these wires to
talk to the signalman. Handy if the radio isn't working on that
bit of the track.

It can also be used to turn off the electricty to the rails in that
part of the track - again, handy if there is a problem.

Not "handy", it was designed that way. In use from the start of the electric
tube railways the Tunnel Telephone is the first option in the event of
needing traction current to be discharged. Pinching the wires together
causes them to short out and operates the cut-outs in the sub-station
Clipping the handset on then allows the driver to talk to the Line
Controller.

Don't forget that train radio is a very recent introduction and is
unreliable compared to a direct line telephone.