Track Circuit Indicators

[David Waite]

A question for the Signaller’s or anyone that might know.
If a section of running line for instance was track circuited in the rear of a home signal and had a banner type Instrument
on the block shelf showing the state of this track circuited section, when the signal was off and a train at speed ran through
the track circuited section would the Instrument hold fast showing the occupied position as the train passed or would it have a tendency to flicker slightly possibly due to poor wheel contact , rail condition (wet/dry) or type of rolling stock.
David.

[Mickey]

I only ever worked ex-Midland boxes and one ex LNWR box on the Euston-Watford DC lines and several other North London line boxes and all those boxes had 'Illuminated track circuits' inbuilt into there track diagrams but I think I know what you mean regarding the track circuit indicators that showed an 'on' or 'off' indication that were mounted on the block shelf. With regards to the 'Illuminated track circuits inbuilt into the box track diagram' I never noticed any problems with them in wet weather, trains occupying a track circuit during wet weather on an Illuminated track diagram still showed occupied continuously.

[thesignalman]

A question for the Signaller’s or anyone that might know.
If a section of running line for instance was track circuited in the rear of a home signal and had a banner type Instrument
on the block shelf showing the state of this track circuited section, when the signal was off and a train at speed ran through
the track circuited section would the Instrument hold fast showing the occupied position as the train passed or would it have a tendency to flicker slightly possibly due to poor wheel contact , rail condition (wet/dry) or type of rolling stock.
David.

I was a Relief Signalman for many years and worked a number of boxes with that kind of indicator - I never saw one flicker.

John

[Mickey]

From memory the old Upper Holloway box on the Kentish Town-Barking line a small old Midland Railway box in origin (1891-1985) had two or three 'occupied/clear' track circuit indicators mounted on the block shelf instead of an Illuminated track diagram I recall on a visit to the box during the early 1980s. Also I can't recall if Neasden Midland Junction box in north west London on the Acton Wells-Dudding Hill branch and another small Midland Railway box in origin which is still there in 2023 if it either had 'occupied/clear' track circuit indicators mounted on the block shelf or an Illuminated track diagram when I worked the box occasionally around 1988-1990 when I was on the relief around the north London line (1987-1990)

[StevieG]

" .... I think I know what you mean regarding the track circuit indicators that showed an 'on' or 'off' indication that were mounted on the block shelf. .... "

Mickey, I think David' Waite's phrase
"track circuited .... and had a banner type Instrument on the block shelf"
is probably referring to the sort of shelf-mounted indicator that in my experience seemed favoured by the GWR/BR(W).

Rather than any sort of 'needle'/pointer with positions labelled just "Clear" and "Occupied", the GW/WR indicators had the word "Track" always visible towards the top left, and a moving red (or black?) bar whose indicating positions were horizontal and inclined at 45 degrees (hence the description 'banner type') ; horizontal for occupied and at 45 degrees - lower quadrant style - for clear, and revealing/obscuring, as appropriate, the words "Clear"(which was usually in green) and "Occupied" (usu. red), such that for occupied the words "Track" and "Occupied" could be read along above the bar, and "Track" (above left) and "Clear" (below right) when the bar was at 45 degrees.

Of course any 'flickering' from poor conductivity between the rails in the TC being occupied situation, could possibly occur regardless of the type and nature of indicating a TC's clear/occupied status.

[David Waite]

Many thanks for your help
Mickey / thesignalman & StevieG
It is something I had no idea about whether or not a mechanical instrument of this type would hold its position without any movement as a train passed, the reason for my question is I am currently building a RE Thompson Banner instrument and this
will be controlled by some form of photo electric or infrared control the problem being is the circuit would be interrupted
due to gaps between the rolling stock so to get a continuous operation is something I must now think about, perhaps multiple sensors in parallel along the track circuited section any ideas are welcomed.
David.

[Mickey]

With regards to track circuiting I was 100% familiar with 'Illuminated track diagrams' although I am still trying to recall if Neasden Junction box on the Acton Wells-Dudding Hill branch had an Illuminated track diagram or was the track circuits shown as occupied/clear 'indicators' on the block shelf when I occasionally worked the box on the relief between 1988-1990?. The next box south of Neasden Junction at Acton Canal Wharf had an Illuminated track diagram when I worked my last shift at the box when I was on the relief back in 1990.

As Stevie pointed out 'poor conductivity' would cause a track circuit to 'drop' (show occupied) when a train wasn't on that particular track circuit and a track circuit failure would usually fall into two categories either a 'Intermittent track failure' or a 'continuous track failure' with the latter meaning the track circuit concerned is showing 'occupied continuously' and is therefore possibly easier for the S&T linesmen to trace the fault and is referred to by the S&T and signalmen as being 'hard down' which they the S&T linesmen like cos they can trace the fault better by putting the S&T electric meter on the length of track/railhead concerned and obtaining a reading of the 'amps' going through the rail and then 'zeroing in' on the fault' and finding what's causing the problem?. The 'Intermittent track circuit failure' can be harder to locate due to it sometimes 'dropping' (failing) and then it 'clears' again by it's self for a period of time before 'dropping' again and then it fails again and so on. Sometimes when all else has been checked in the nearby relay room i.e. circuits and relays and nothing has been found the last resort to finding the problem with a continuous or Intermittent track circuit failure will be for the S&T linesmen to 'walk the length of railway' concerned that the track circuit has failed in or keeps intermittently failing in and try and discover what's causing it?. In warm/hot weather a usual problem that can cause either an Intermittent or a continuous track circuit failure is a 'worn out' plastic T-piece at a insulated block joint' (where two rails are fastened/joined together with a insulated fishplate) and the metal rail ends are 'touching each other' causing a 'track circuit failure' that was a 'common occurrence' that caused 'track circuit failures' during hot summers on the railways at various locations.

[StevieG]

" .... As Stevie pointed out 'poor conductivity' would cause a track circuit to 'drop' (show occupied) when a train wasn't on that particular track circuit .... "

Mickey,
to possibly help David Waite's understanding, my wording - "Of course any 'flickering' from poor conductivity between the rails in the TC being occupied situation, could possibly occur regardless of the type and nature of indicating a TC's clear/occupied status." - perhaps could have been better.

I was trying to refer to the opposite situation of when a TC section is actually occupied (by a train, etc.), but the TC indication might 'flicker' briefly to 'Clear' because of poor conductivity in the short-circuiting of the TC between the two rails via the train's wheels/axles; most probably owing to poor rail-wheel contact, e.g. railhead/s (or wheels) being contaminated by leaf build-up or rust.
No TC indication method that I know of includes any means of maintaining an indication of 'Occupied' when its circuitry from the lineside is, even momentarily, detecting it as clear. To include that could possibly 'disguise' a train detection problem developing, effectively hiding from the signalman the risk of it developing into the 'wrong side failure' situation of a TC showing 'Clear' when actually occupied, for longer periods.

[Mickey]

As previously posted I am or was only more familiar with track diagrams with 'Illuminated track circuits' built into the track diagrams and as for any wording on those TC indicators I was just assuming the 'logical' wording of them having either 'clear' or 'occupied' shown on them but as I previously posted I wasn't that familiar with individual TC indicators at all.

As for a "track circuit failure" it should only be referred to or be called a "track circuit failure" after it has been positively established that it IS a track circuit failure and to not just be assumed by a signalman that it is a track circuit failure because when a track circuit shows 'occupied' (or has dropped) for no apparent reason on a signal box track diagram it should always be assumed that the track circuit is "working correctly" and is showing 'occupied' for a reason because there could be the proverbial '5-ton bulldozer' sitting in the 4ft and an OBSTRUCTION ON THE LINE!!.

[Mickey]

Also I can't recall if Neasden Midland Junction box in north west London on the Acton Wells-Dudding Hill branch and another small Midland Railway box in origin which is still there in 2023 if it either had 'occupied/clear' track circuit indicators mounted on the block shelf or an Illuminated track diagram when I worked the box occasionally around 1988-1990 when I was on the relief around the north London line (1987-1990)

From my old NUR diary (National Union of Railwaymen) that I kept while I was a relief-signalman on the north London line (1987-1990) to keep a recorded note of my weekly orders at various boxes apparently the last time that I worked Neasden Junction box was in May 1990 and by that time the box was 'fringing' with Marylebone at Neasden South Junction and still working Absolute block with both Dudding Hill and Acton Canal Warf boxes on either side as it still is today in 2023.

[David Waite]

Another question regarding the Banner type Track circuit Indicators
What would be the most common way of labelling this type of Instrument on the block shelf, numbers or letters or both.
Would I be correct in the following.
By the same number of the signal post if this was in advance of the track circuit that the Indicator was being controlled by.
If so and there were no signals at the track circuited area that the instrument was being controlled by how would you label it?
I hope that makes sense.
David.

[StevieG]

Another question regarding the Banner type Track circuit Indicators
What would be the most common way of labelling this type of Instrument on the block shelf, numbers or letters or both.
Would I be correct in the following.
By the same number of the signal post if this was in advance of the track circuit that the Indicator was being controlled by.
If so and there were no signals at the track circuited area that the instrument was being controlled by how would you label it?
I hope that makes sense.
David.

On BR's Western Region David Waite, I saw two methods of TC identification, (but that may not have been all methods).

AFAIR, things were as follows.

Where I saw their banner-type TC indicators in use, during the 1960s/early '70s (but at least some would have dated from much earlier), --
-- where one TC was the only one covering some or all of the track between two stop signals of the same box, the TC would be numbered xT, where x is the number of the 1st signal, in rear of the TC (the TC showing occupied would have locked that signal's lever at Danger, stopping it from being pulled with a train ahead).

If there was more than one TC between two such signals, then (IIRC) the one nearest the 2nd signal was numbered as above, with the other one(/two etc.) being the same but with a prefix letter, i.e. AxT [and if there was a third, BxT, and so on]

For a TC on the approach to a signal with no previous stop signal of the same box, it was xAT, the x being the number of the signal being approached, and the A presumably standing for 'approach'.

One exception to the above, I think, was where a TC was provided to lock a Facing Point Lock lever to prevent it being moved to unlock facing points with a train approaching or on the points, in which case the TC could instead have the identity xT, where the x was the number of the FPL lever.

The other BR(W) method I saw was usually where TCs had been put in during later times (perhaps WWII times or 1950s etc.), often when a scheme of several TCs were put in at the same time to form a more comprehensive TC coverage of the area around the box's points and signals, and where the TCs were usually indicated by lights on an illuminated diagram rather than by banner type indicators.
These tended to be numbered (actually, lettered) sequentially by line and in the order in direction of normal travel ; e.g. for one line, AA, AB, AC, etc., and another line, BA, BB, BC etc.

Hope at least some of the above is of help.

As I said before David, I only saw banner-type indicators in boxes of BR Western Region, and I know of no other Region or predecessor company that used them rather than any other type of shelf-mounted indication, but that doesn't mean that there was no such other area.
P.S. I've now an idea that BR's London Midland Region MAY have also used banner-type indicators but with black 'banners' rather than red.
But they, and their predecessor LMSR company, used one or more very different TC numbering methods, which I can't help with.

[David Waite]

Thanks StevieG
That’s very helpful, in my case the Banner instrument is for a TC at a outer home signal so there for as the distant signal is 1 the Track circuit and the instrument would be known as 2AT and a label of the same placed under the instrument where it’s mounted on the block shelf is this correct.
David.

[StevieG]

" .... and a label of the same placed under the instrument where it’s mounted on the block shelf is this correct
David."

If the indicators were of what became a fairly standard-sized circular type also used for repeating signals, colour-light signal power supply status, motored-points positions, etc., with black-looking bakelite-like cases, then I think the TC indicator IDs were done in the same way, i.e. on a small white ivorine or traffolyte disc inside, milled out to the black level, and fixed to the upper part of the vertical brass piece which incorporated the moving part's pivot.
But quite by chance, thanks to a visit to Didcot Railway Centre yesterday, I was reminded that early GW 'banner' TC indicators (when, perhaps very roughly, around 100 years ago, a box might have had only very few or just one TC [ many would still have had none ] ), usu. having circular brass cases of varying sizes, TC IDs then could be by description rather than having a number, which could be found painted along the red 'banner', or on a rectangular plate - often brass - affixed to the top of the indicator.