Greetings, Group.

On a recent trip to London, I happened to be looking out the windows of a
tube train on a deep level track, and noticed a pair of what appeared to be
unshielded, uninsulated copper wires, approximately 8 inches apart from each
other. They were mounted above the usual cables you see inside a tunnel, and
were considerably thinner - just think 30amp cooker cable. (At least, that's
how they looked.)

They'd appear to terminate a few meters before a station. Whereas the larger
cables would appear to either go down below platform level, or behind the
advertising boards, I was unable to see how these terminated - they simply
disappeared.

Can someone cast some light on what these two wires are and do?
Also, purely out of curiosity, what -do- all those thick cables do? I always
assumed tube trains were hooked up to the power and negative tracks.

Thanks in advance,
Dave
---
(remove spamblock or reply to group)

On Tue, 16 Sep 2003 02:27:15 +0100, David Baxter

wrote in :

On a recent trip to London, I happened to be looking out the windows of a
tube train on a deep level track, and noticed a pair of what appeared to be
unshielded, uninsulated copper wires, approximately 8 inches apart from each
other. They were mounted above the usual cables you see inside a tunnel, and
were considerably thinner - just think 30amp cooker cable. (At least, that's
how they looked.)

They'd appear to terminate a few meters before a station. Whereas the larger
cables would appear to either go down below platform level, or behind the
advertising boards, I was unable to see how these terminated - they simply
disappeared.

Can someone cast some light on what these two wires are and do?

From my readings on this group, they serve two purposes: when
shorted out, they cut traction current to the live rails; they also serve
as a telephone circuit so a driver can clip a handset to them to
communicate with a controller (I'm not sure if the electrical load of the
handset is enough to shut off traction current).

--
Ivan Reid, Electronic & Computer Engineering, ___ CMS Collaboration,
Brunel University. Room 40-1-B12, CERN

David Baxter wrote:
Greetings, Group.

On a recent trip to London, I happened to be looking out the windows
of a tube train on a deep level track, and noticed a pair of what
appeared to be unshielded, uninsulated copper wires, approximately 8
inches apart from each other. They were mounted above the usual
cables you see inside a tunnel, and were considerably thinner - just
think 30amp cooker cable. (At least, that's how they looked.)

They'd appear to terminate a few meters before a station. Whereas the
larger cables would appear to either go down below platform level, or
behind the advertising boards, I was unable to see how these
terminated - they simply disappeared.

Can someone cast some light on what these two wires are and do?
Also, purely out of curiosity, what -do- all those thick cables do? I
always assumed tube trains were hooked up to the power and negative
tracks.

R M S posted the following reply this morning, but on the wrong thread:

See:

http://www.trainweb.org/tubeprune/tr...ephone%20Wires

for a description on what the window height, copper wires are for. (You may
have to copy and paste the link if it breaks into two lines)

R M S


--
Richard J.
(to e-mail me, swap uk and yon in address)

David Baxter wrote in message ...
Also, purely out of curiosity, what -do- all those thick cables do? I always
assumed tube trains were hooked up to the power and negative tracks.


Depends which cables you mean really - the *really* think black ones are the high tension ones which deliver AC at 11kV from the Bulk Supply Point to the substations, from where it is transformed and rectified to 630vDC for supply to the current rails.

The rest serve a range of things including lift and escalator supply, lighting, telephones, clocks, signalling, train radio leaky feeder etc. It's not uncommon also for many of the cables you see to be redundant.