Re: First Automatic signal?

[signal_spotter@my-deja.com]

>
> Yes, The current way the Interlockings are arranged, the amount of
> crossboundary telegrams
> has led to timing problems.
>
> Plus, one interlocking failure will guarantee the shutdown of traffic
> through the area. The boundaries
> should have been along Main/Suburban lines. (The benefits of
hindsight!)
>
> Yeerongpilly as an installation really can't be improved boundary
wise, and
> South Brisbane needed to
> get the souped up Alstom MPM's to keep it running with the last
additions.
>
> As a system, the SSI has yet to impress. The problem is, it's the
only CBI
> that can handle the size,
> which doesn't say much for CBI's vs Relays.
>
> Peter Dwyer
>
>
Putting the boundary along the main/suburban as suggested would have
been looked at. We look at all possibilities for Cross Boundary
allocation and come up with the one that has the least telegrams (or at
least the simplest). It's possible that a boundary through the
main/suburban may have meant that it would pass through points which is
more complicated and could lead to more timing problems. Check out the
SSI data prep guide Chapter on "Communications with Other
Interlockings - Cross Boundary through a set of points" and see how
complex that is compared to a simple straight line. As for one I/L
failure tying up the yard, well, how often has it happened. Roma St SSI
has been in for 5 years now. And just ask the Sydney commuters what a
simple air leak or a conventional relay "sticking up" does to the rail
network. I'm sure you've read the gripes in this news group over the
past few weeks. There is always going to debate over CBI vs RRI. The
solution is not to make SSI bigger to cope, it's to make the signalling
system simpler instead of over-engineering. And it happens down here in
Sydney too. Hornsby is so over-engineered that the volume limits of the
eprom were exceeded and I had to not only reduce the data volume by
normal reduction techniques (ie subroutines), but had to remove some of
the functions from the SSI (point setting) and do them in the PMUX.
That was just to get it to fit. So signalling engineers really need to
go back to the drawing board when designing a layout instead of adding
all the bells and whistles they can think of and expecting the CBI to
cope.

regards Ian
Signal Design Engineer


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