London Underground Question
Discussion
Someone might know:
1. On the tube there are two wires that run at window height, I seem have it in my head someone told me these were for the driver to attach a 'phone' (or handset) across these to speak to a control room as a backup for the radios? However someone else said the driver can either 'pinch' these together or bridge them with metal which would kill the power to the track.
2. Which leads on to the question of killing power to the track, I also thought that the driver's cab had a bus bar? (if thats the right term), which he can short the rails out ?
Been looking on google for ages and havent come up with anything...
Out to the ph massive
1. On the tube there are two wires that run at window height, I seem have it in my head someone told me these were for the driver to attach a 'phone' (or handset) across these to speak to a control room as a backup for the radios? However someone else said the driver can either 'pinch' these together or bridge them with metal which would kill the power to the track.
2. Which leads on to the question of killing power to the track, I also thought that the driver's cab had a bus bar? (if thats the right term), which he can short the rails out ?
Been looking on google for ages and havent come up with anything...
Out to the ph massive
Yes & Yes.
The two wires are the 'tunnel telephone' system. I did some consultancy work on that & other systems many years ago.
The wires have a dual purpose. They can indeed be pinched together - that signals an alarm & kills the traction current. (It also has a habit of giving the driver a mild shock apparently!). It can be a bit fiddly to get to work as the wires get covered in crap.
So once the driver's shorted the wires to signal an alarm & remove the traction current, he can then attach a field telephone via croc clips & talk to control.
As a separate item, there's a shorting bar that can be laid across the tracks to ensure that the current can't come back on iirc.
I don't know if the TT system is still in use. Radio coverage has been improved by use of leaky feeder so I'd hope that drivers have proper comms these days - but you never know!
The two wires are the 'tunnel telephone' system. I did some consultancy work on that & other systems many years ago.
The wires have a dual purpose. They can indeed be pinched together - that signals an alarm & kills the traction current. (It also has a habit of giving the driver a mild shock apparently!). It can be a bit fiddly to get to work as the wires get covered in crap.
So once the driver's shorted the wires to signal an alarm & remove the traction current, he can then attach a field telephone via croc clips & talk to control.
As a separate item, there's a shorting bar that can be laid across the tracks to ensure that the current can't come back on iirc.
I don't know if the TT system is still in use. Radio coverage has been improved by use of leaky feeder so I'd hope that drivers have proper comms these days - but you never know!
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