In message , Steve
Dulieu writes
The one in the middle is the negative and carries the lower voltage of
220v, the one furthest from the platform is the positive and carries
the higher voltage of 440v for a combined total of 660v. The other two
rails (the ones not on insulators) do in fact have a slight electrical
current in them to work the signals (somewhere between 5 and 10 volts
IIRC).
The outside rail is positive and the centre rail is the negative with a
potential of 630v between them though there has been discussion on here
as to whether its a 420/210 split or a 630/0 split. The running rails
carry a.c. Voltages of between 5 and 10v but there can be up to about 30
track circuits at some places. So the running rails can potentially
carry a tingle at some points.
--
Clive