Re: Signalling queries

[Eddie Oliver <eoliver@efs.mq.edu.au>]

Chris Downs wrote:
> 
> Resignalling occurred in the mid 1980s, 1985/1986 from memory?  It was
> certainly done prior to the opening of the East Hills - Glenfield line, I
> thought by a year or two.

I have a vague recollection of it being done in phases, the first to
ensure that Glenfield was covered and the second to finish off (from
Ingleburn??) to Leumeah/Campbelltown. However I can't recall whether the
separation between the phases was weeks, months or years.

> Now my chance to perhaps clear up some history.  Many of the signals on the
> Liverpool - Campbelltown section were single light search light signals prior
> to the most recent resignalling.  I thought that jointless track circuits were
> used for the 2nd most recent resignalling which was done in conjunction with
> Liverpool - Glenlee electrification for 1968 opening?  These circuits included
> two large cable loops that formed a rough square between the rails.

The cable loops were the early versions of the inductive/capacitive
loops which separate the different frequencies in the adjacent circuits,
i.e. the equivalent of insulated joints in jointed track circuits. These
things have become much more elegant in recent times (and again I mean
"recent" in relative terms, not as in last week/month/year).

For people who don't know what we're talking about, there are many
sections of track  where it is very easy to see the equipment for these
changeover points. There are typically two boxes (often silver in
colour) standing adjacent to the tracks above rail level, and about 20
metres apart; there is usually a third box of slightly different type
half-way between them. The boundary between two adjacent track circuits
can be regarded as the centre of this layout, although they can
conservatively be regarded as overlapping anywhere between the two
outermost structures, in the sense that a wheelset occupying the track
between those two structures might be sensed by both the circuits
simultaneously.

> I also thought the signalling was replaced in the '80s for more than one
> reason.  Better headways were needed for the extra services travelling via
> East Hills plus ongoing traffic growth.  I thought there was a specific
> urgency on this line because the traction equipment on the chopper cars (for
> which delivery commenced on 198?) interfered with the track circuits on the
> Campbelltown line.  The C3581-3582 certainly spent a long time in trials with
> C3583-3584 entering service 1st.

There is always a fear that new trains will interfere with track
circuits, and the specifications for tangaras and the millennium trains
have all sorts of conditions about non-interference not only with track
circuits but also with communications systems. However I have never been
able to find anyone who could confirm that the chopper sets actually DID
interfere with track circuits, as distinct from people fearing that they
might. Anyone have any more definite information?

> Erricson's ATC was also trialled between Campbelltown and Liverpool (some of
> the yellow bailises (sp?) 

balises

> are still in place in the 4 foot) with a Tangara and
> an 86 being fitted with ATC equipment.  I thought the trial results were mixed
> and for that reason, + $$, ATC was not pursued.

It was a very fragmentary "trial".