Re: Insulated Rail Joints.

[signal_spotter@my-deja.com]

In article <39bc9afb$0$24865$7f31c96c@news01.syd.optusnet.com.au>,
  "B." <gunzel412@dingoblue.gunzel.net.au> wrote:
> Mark Bau <markbau@altavista.com> wrote in message
> B5E1F389.15CDA%markbau@altavista.com">news:B5E1F389.15CDA%markbau@altavista.com...
>
> >> You may notice, around points, steel boxes (about 1m sq)
> >> mounted on posts. These are Impedance Bonds and their
> >> purpose is to allow the 1500v traction return current to
> >> flow around the Block Joint but still provide electrical
> >> isolation for the track circuit.
>
> > Similar to a tuneable joint coupler where a track circuit
> > like for a road crossing has to go through an insulated
> > joint.
>
> Except the Impedance bonds pass DC, and block AC, where as the joint
> couplings of whatever flavour pass AC, and block DC.
>
> Tunable joint couplings?  You must have Coded Tracks... |-)
>
> Back to those original IRJ's, why again do you need then at a plain
buffer
> stop?  Wouldn't you just have one impedance bond, tie the 2 rails to
it, and
> the centre tap to the crossbond?
>
> --
> B.
>
> Email - gunzel412 at dingoblue dot net dot au
> ICQ#  - 82329734
> Phone - long, long, short, long.
>
>
Electrically it will work but it's an SRA requirement to put joints in
the ends of a dead end siding. That guarantees an isolation and not
relying on the ends of the rails not shorting together. So as a result
the rails on the track circuited side are tied via a cable (if it's
Single Rail Jeumont Schneider TC) or via an Impedance Bond (if it's a
Double Rail Jeumont Schneider TC). The other end of the dead end siding
is just cable bonded together.

regards Ian
Signal Design Engineer


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