Re: [NSW] Granville question re signals

[David Johnson <trainman@ozemail.com.au>]

signal_spotter@my-deja.com wrote:

> In article <itbw5.16813$cr3.444008@ozemail.com.au>,
>   "Chris Downs" <cvdowns@ozemail.com.au> wrote:
> > I stood at the Sydney end of Granville's platforms 1 & 2 for  half an
> hour
> > last night.
> >
> > Watching OP yo-yos on the up main they were leaving Granville and
> running
> > express to Lidcombe.  Four up main signals are visible, Granville up
> main
> > starter (1), up main intermediate before Clyde (2), Clyde up main
> starter
> > (3) and the following up main signal (4) on the way to Auburn.
> >
> > When a train leaves Granville on no occassion did sig 1 clear before
> sig 2.
> > I assumed sig 1 was being hald at danger by the signaller but
> continued
> > observation suggested this wasn't necessarily the case.  Once the
> train is
> > well on its way to Auburn the aspects shown at 1=G/Y, 2=G/Y, 3=G/R &
> 4=R/R.
> > 1 & 2 show the same aspect due to the short distance between 3 & 4.
> The
> > part I don't understand however is that 2 when from G/Y to G/G several
> > seconds before 1 went from G/Y to G/G every time.  The result was a
> sequence
> > of four signals showing G/Y, G/G, G/Y & G/R.
> >
> > Does anyone know why this is so?
> >
> > Ta
> >
> > Chris
> >
> >
> Possibly due to the delay in processing. (1) signal would look at (2)
> at G/G before stepping up to G/G in the logic.
>
> ie The SSI data for S1 aspect sequence would look as follows:-
>
> G s 73                 (R/R)
> if S2 set <y           (test for S2 memory at 'better than G/R')
> then G s 5             (drive top green lamp ie output 5)
>      G c 7             (turn off top red lamp)
>      if S2 set fyy     (test for S2 memory at G/Y)
>      then G c 3        (turn off bottom red lamp)
>           if S2 set g       (test for S2 memory at green)
>           then S1 set g     (set S1 signal memory to green)
>                G s 1        (drive bottom green lamp)
>           else S1 set fyy   (set S1 memory to G/Y)
>                G s 2        (turn on bottom yellow lamp)
>           \
>      else S1 set y          (set S1 memory to G/R)
>      \
> \
>
> Hope this helps.

Okay, whay then, in Low speed areas does the Low speed light go off before the
top green comes on, exaggerated by the delay in proving the trip lowers?  At
some locations, the low speed light goes off some 3 seconds before getting a
caution indication.   This scares the crap out of you when approaching a home
signal at 25 km/h and it goes back to stop.

--
David Johnson
trainman@ozemail.com.au
http://www.ozemail.com.au/~trainman/
------------------------------------
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