Re: Three Position Signalling

["Exnarc" <gwrly@netspace.net.au>]

Christopher_Martin GORDON <cmgord@ecr.mu.oz.au> wrote in message
7sus6d$t8b$1@mulga.cs.mu.OZ.AU">news:7sus6d$t8b$1@mulga.cs.mu.OZ.AU...
> Three Position Dwarf Signals:
> For a three position dwarf signal (at Caution, yellow) is it once the
> train passes the signal it will revert to stop? Or the back of the train.
> (I am assuming here the signal is controlled by track circuit and lever)

Once the first vehicle passes the signal, although at some locations the
signal would remain at caution until the lever was put back in the frame,
Dandenong was one of these locations (3 position target Dwarfs in this
case).

The essence is the meaning of the aspect:
Low Speed Caution, "Points are set for the movement, section may or maynot
be occupied". Where as a Clear Low Speed, indicates that the "Points are set
for the movement, the track section is clear and the next fixed signal is
displaying a proceed aspect". In the case of the latter on ATC and CTC once
the train is clear of the points onto the Mainline the Driver may resume
track speed. For some reason this doesn't apply on ABS such as Bayswater
when the speed must not increase until the train reaches the next signal,
(an Auto over a km away).

>
> What about a dwarf signal showing Clear, (green) like at Baywater,
> Camberwell, Burnley.  Does the train put this signal back to
> Caution or Stop? (i thought Caution).  Like would it be once the train
> passes the signal it goes back to caution, then once the back of the
> trains or the lever is restored the signal will revert to stop?

Back to stop, when the first wheel hits the track circiut, there would be no
point init going to yellow then red after the train was fully passed the
signal!!!
I have never rushed back to check, but I'm sure that is the case.

>
>
> Where they any signals ever that showed red/red/green?  Like at the
> orginal South Yarra (ie first Three Position Signalling).
> I know many other things like all interlocked signals being homes
> was only done at South Yarra (the others became controlled automatics)

Clear Low Speed. On Home Signals the old rule book showed R/R/G as a Clear
Low Speed. I've never seen one in 37 years, and they have now been removed
from the rules.

>
> What about all the repeating signals? ie before the first Automatic
> is that only the case for places like Somerton, St Albans, (ie places
> from two position signals to three position signals).  Was it
> at South Yarra that all the first automatics had repeating signals
> even if the previous station had three position signals?
>

There are a lot of locations with Repeating Signals other than when going
from a 2 position to a 3 position area.

Broadford had one that repeated the Down Distant, there was one in the old
Melbourne Yard that showed Y/Y, G/Y and Reduce to Meduium Speed.

Emu has one that repeats the Trailable Point Indicator, Paisley has one that
protects a Switch Lock Siding on ASW. The Repeating Signal is a very hand
tool to solve problems at many locations.

> Last thing what is the colour of the arm for a repeating signal?
> Like if the signals at St.Albans, Somerton were semaphores.
> (Just a top arm, and yellow market light).

The arm would be Yellow, the only one I've heard about was on the Maldon
line. (Seen a photo, it went many years ago).

> --
>
> Chris Gordon
> http://www.ecr.mu.oz.au/~cmgord
>
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