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'[OT] choo choo signals (was RE: Car LED lighting s'
1999\07\28@202359 by Anne Ogborn

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Michael Rigby-Jones wrote:
>
> I used to work for ABB Transportation who made these things so I should
> really know....but it's been a while :o)
>
> I *think* the yellow aspect meant something like the next block section but
> one is occupied so proceed with caution?
>
> Also the red aspect is on the bottom, so that there is no hood from another
> aspect underneath that snow could build up on and obscure the signal.  I
> think.
>
> Cheers
>
> Mike Rigby-Jones
>

Wow - the red on bottom is snow related is interesting.

OK - Rr signals are one of three things (simplifying a bit).
They can be block signals, CTC signals, or interlocking signals).

block signals have 3 aspects, red means stop then proceed, yellow means
basicly that the *next* signal is red, so go slow enough to stop before it,
and green is clear.  They are simply an additional safety appliance, and don't
overrule train orders.

CTC signals are operated from a central console, and do replace train orders.
Instead of written train orders, the dispatcher manually sets blocks to green
to allow trains through (they automaticly snap back to red when it passes).

Interlocking signals are at junctions, and signify the position of the various
track switches and whether various tracks are cleared through the junction.
They used to be controlled by guys in towers using cool mechanical computers
as a safety check, but nowadays they're usually controlled by CTC.

The computers (drifting back towards PIC topic), acutally logic machines,
called interlocking plants, used a system of vertical bars connected to
manual levers, and a system of "dogs" - horizontal sliding bars - to
"interlock" them.
It was interesting because it was a 'change' system. Each lever in each
state would lock or unlock some of the other levers.
     If A, then B and C cannot change state
     If B, then A and C cannot change state
Levers controlled signals and turnouts. Some of the levers were controlled by
treadle switches activated by trains, the rest by the operator.

Most of the logic was of the 'prevent a bad thing' variety -
Don't allow a switch to be thrown while a train is detected in that block.
Don't allow a signal to be cleared while a turnout is thrown against the track.

Most of the alternate uses of yellow are in conjunction with interlocking -
various flashing yellow/red combinations indicate safe to proceed at various
speeds through diverging route.

--
Anniepoo
Need loco motors?
http://www.idiom.com/~anniepoo/depot/motors.html

1999\07\28@233045 by Dennis Plunkett

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At 17:20 28/07/99 -0700, you wrote:
{Quote hidden}

don't
>overrule train orders.
>
>CTC signals are operated from a central console, and do replace train orders.
>Instead of written train orders, the dispatcher manually sets blocks to green
>to allow trains through (they automaticly snap back to red when it passes).

The "DRIVER" doesn't know the difference between a CTC section and a BLOCK
section, unless written train orders are in hand. Signals DO override Train
orders, unless that order has been pased by the owner of the section to
"Ignore that ONE" signal i.e. An order must be given for each signal point
within the section.

You should see the mess when you try to go the wrong way down a section.

>
>Interlocking signals are at junctions, and signify the position of the
various
{Quote hidden}

track.
{Quote hidden}


'[OT] choo choo signals (was RE: Car LED lighting s'
1999\08\07@070853 by paulb
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Anne Ogborn wrote:

> Interlocking signals are at junctions, and signify the position of the
> various track switches and whether various tracks are cleared through
> the junction.

 Mmm.  The twin-three-aspect signals used in Metropolitan Sydney with
which I grew up (befriended the local (Tempe) stationmaster and got to
look over the signal house once - a terrific buzz for a young devotee of
logic), use amber in the "home" set to indicate *either* "stop" in the
next block *or* a switch.

 Amber in both "home" and "distant" uniquely indicated a double switch
(or maybe just a single switch - it's a while since I lived there now!),
not to be confused with green-amber which simply indicated green-red in
the next block.

 Then there was the 1/3 size (irised) green "calling-on" aspect which
permitted a train just to clear the station or such.  7 aspects - that
was my favourite.

 Sigh.  If I ever get back into modelling, it will be in "N" or "TT"
gauge.  Grain-of-wheat bulbs are passŽ nowadays, SMD LEDs rule.  You can
even make the *back* of the aspect look true-to-life!
--
 Cheers,
       Paul B.

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