On 22/09/10 11:55, Recliner wrote:

I don't think it was ever more than a plan. And I think originally it
was only going to work in stations, not the tunnels between them.

I'm almost certain there were at least plans to have it work in the
tunnels, because I remember the discussion of leaky feeders at the time.

Basically, you run a piece of coax along the tunnel (that's the feeder),
and at intervals the shielding is removed from a short length of coax,
which causes the feeder to leak RF (i.e. act as an antenna).

-roy