RailWest

...or perhaps you just got the polarity the wrong way round? After all, they are Diodes :-)

But...what then happens if a shorter train goes from L to R and never reaches the relocated B? In effect the system needs to detect 3 conditions:- 1. Train approaching (strike-in) 2 Train passing over the point (continuous detection) 3. Train clear of the point (strike out) 1 and 3 are easy, it's the 2 that may be harder :-)

I'm confused now :-) As drawn, your uni-directional line is for traffic moving from L to R. The LOS board, as drawn, applies to 'wrong direction' traffic from R to L. Clearly you do not want the traffic moving from L to R to be still over the point when it moves back to normal. But if traffic goign 'wrong direction' from R to L inadvertently passes the LOS board, then why would the points be moving anyway? And if they were, and the train was derailed, well isn't that purpose of the points anyway?

Well, the first thing that seems 'obvious' - unless I've misunderstood something - is that if B is only 2" beyond the point, then as soon as the front of the engine passes over the point will start to reverse again long before perhaps even the engine, let alone the first carriage, is clear of the point. What you need to create IMHO is the equivalent of a track-circuit extending from A to B, so that once the train runs onto the pseudo-TC at A the point reverses and is then held reverse by the continued occupation of the TC until its tail end clear the TC at B. Maybe several 'A's at intervals between A and B would do the trick ?

What diagram please?

It should be noted perhaps in this context that, where a signal 'height' is quoted in some official document (eg a Signal Instruction or similar), AFAIK the practice was for the figure quoted to relate to the height of the arm above the rail head. The actual post of course would extend some (variable) distance further above the arm, and if the post was set back some way from the track on an downward-sloping embankment than the visible part could be even longer still. Conversely, some signals quoted with a relatively high-ish height might actually be quite short posts, but stuck high up on the side or top of a cutting.

No need to nudge, I'm here already....:-) I would agree that the PSR shows 55. Sadly I don't have the answer to the signal post height, as such details are not recorded in any known records other than occasional references to replacements in some Signal Instructions. I know that at least one S&DJR simulation was produced a few years ago, so maybe the author of that (is 'author' the right term, or could it be 'creator' perhaps) may have the answer already.

I've broadened my research now to include the S&DJR's use of Electric Repeaters in general (not just Arm and Lamp) and an initial write-up can be found here for those who are interested:- www.trainweb.org/railwest/railco/sdjr/sigmisc.html#repeaters Comments, corrections and extra information always welcome ! Admittedly there is a lot more to this subject, especially with the early years, but I don't really have the time at the moment to delve into all the ramifications in details. Primarily I just want to write-up a 'general overview' for those who may want a simple explanation of the basics.

I've broadened the topic now to Electric Repeaters in general and an initial write-up can be found here for those who are interested. www.trainweb.org/railwest/railco/sdjr/sigmisc.html#repeaters Comments, corrections and extra information always welcome !

>>> What you really want is not the box diagram - it's the wiring diagrams for the box - but those are almost invariably long gone. Sadly, you are right - almost none are known to exist, and those that do are merely for parts of the installation :-( >>> You can't rely on diagrams even today to tell you whether a signal is repeated.... I think that depends upon age and BR Region. Certainly IMHO it seems to have been standard BR(S) practice to include such detail on box diagrams, whereas BR(WR) never did (which is not helpful when they replaced some of the S&DJR diagrams). >>> What is more commonly shown on diagrams is "HNC" (Home Normal Control).... Not something that I have ever seen on SR/GWR diagrams, though I know that it was done elsewhere. To be honest, apart from 'upgrades' done in the Templecombe Jcn area, most S&DJR double-line boxes did not even have 'Line Clear' releases and even 'Tablet Out' releases were not universal on the single-line sections until quite late, so I doubt that they had much by way of 'sophistication' in their controls. >>>..sometimes a whole set of lamps would be connected in series and indicate on a single repeater...... There were 3 instances of that practice that I have found so far on the S&DJR.

[Cross-posting from the S&DJR forum.] I am researching the extent to which the S&DJR provided Arm and/or Lamp Repeaters in their signal-boxes (and some GFs.) This is not an easy subject to examine, as most of the detail comes from information listed on signal-box diagrams, a practice which does not seem to have become common until about the 1930s. Even in the 1950s some diagrams had no such detail at all, but its absence can not be taken as a definite indication that no such repeaters were provided - it may be just that the original diagram negative was never updated. My general impression is that initially the provision of Arm Repeaters was limited to Distant signals (not surprising perhaps, given their remote locations) and even then not all of those. Arm repeaters for Stop signals did exist in later years at some locations, possibly because of signals being moved further out; there were also a few provided on signals which IMHO should not have needed them, so maybe it had become the practice in BR days to provide them as a matter of course when making alterations? Lamp Repeaters appear to have been very scarce - initially I found only six! Even Distant signals did not appear to have them as a rule, which I find strange - after all, if a train is approaching at night and the lamp is out and the driver has lost his bearings, then he's going to get a shock when the first he sees is the red light from a Home signal, so that extent I would have considered Lamp repeaters perhaps to have been even more important than Arm repeaters for Distant signals. Although quite a few photos do exist of S&DJR signal-box interiors which show some repeaters, it is not always easy to determine their function and to which signal(s) they apply. Often the photos show only part of the instrument shelf anyway, so the record is incomplete. Any thoughts and/or S&DJR-specific information would be appreciated - thanks!

I am researching the extent to which the S&DJR provided Arm and/or Lamp Repeaters in their signal-boxes (and some GFs.) This is not an easy subject to examine, as most of the detail comes from information listed on signal-box diagrams, a practice which does not seem to have become common until about the 1930s. Even in the 1950s some diagrams had no such detail at all, but its absence can not be taken as a definite indication that no such repeaters were provided - it may be just that the original diagram negative was never updated. My general impression is that initially the provision of Arm Repeaters was limited to Distant signals (not surprising perhaps, given their remote locations) and even then not all of those. Arm repeaters for Stop signals did exist in later years at some locations, possibly because of signals being moved further out; there were also a few provided on signals which IMHO should not have needed them, so maybe it had become the practice in BR days to provide them as a matter of course when making alterations? Lamp Repeaters appear to have been very scarce - initially I found only six! Even Distant signals did not appear to have them as a rule, which I find strange - after all, if a train is approaching at night and the lamp is out and the driver has lost his bearings, then he's going to get a shock when the first he sees is the red light from a Home signal, so that extent I would have considered Lamp repeaters perhaps to have been even more important than Arm repeaters for Distant signals. Although quite a few photos do exist of S&DJR signal-box interiors which show some repeaters, it is not always easy to determine their function and to which signal(s) they apply. Often the photos show only part of the instrument shelf anyway, so the record is incomplete. Any thoughts and/or location-specific information would be appreciated - thanks!

Even shorter perhaps, circa-1900 the Up Distant for Highbridge 'A' box was underneath its own Up Home! Admittedly the latter was slotted as the Up Home for Highbridge 'A' and also 'B' had 'control' over 'A's Up Distant.

Ah well, that would fit Henstridge then :-)

...but none on the S&DJR :-)

A distinction apparently not employed at Henstridge on the ex-S&DJR, where white marker lights appeared circa-1955 but the siding points remained in use until 1965 :-)

But the diagram for Penwithers Jcn would not show whether the distant belonging to another box was fixed or not - that would be shown only on the diagram of the other box.

There is a SLS photo from 1936 which clearly shows the disc 7 some distance in advance of the Down Home, so presumably (not visible in the photo) close to the point toe (or end of the FPL locking bar).

I would agree with the Stationmaster as regards using just a single yellow disc (or perhaps the miniature-arm version thereof). The GF seems totally unnecessary. I'm dubious about the need for a BR for sighting simply by trains coming out of the bay or goods yard, as any such trains are going to be moving slowly enough that IMHO a delay in sighting the actual stop signal is unlikely to be a problem.

What is the purpose of the facing crossover? Such things were usually avoided like the plague unless absolutely necessary. If the sidings at the bottom are for goods, then how can anything coming across the facing crossover into the yard do any shunting when there is no run-round facility. If the 'DMU line' at the top is for passneger traffic, then there needs to be a trap-point at the exit from the loco yard to protect it. Rule 1 - work out your layout signalling before you start laying any track, it avoids a lot of messy alterations later :-)

Actually, it was neither ! The line from the goods yard crossed the Down Main by a plain diamond crossing and connected into the Middle Siding only.

Errr.....that's the new TT in the New Yard, not the old one in the goods yard.

AFAIK that turntable was removed when the new one was installed in yard at the Junction. I'm not aware of any photo of it. As late as 1930 the points (No 10) leading into the goods yard were still known as the Loco Yard points.

Prompted by the emergence of that photo, I've done a few updates to my 'signals' web-page . Mostly about ground signals and such topics as those used as repeaters and the various methods used to 'elevate' some. To a large extent such variations do not appear in official records, so they only come to light when a suitable photograph turns up at random somewhere.....so keep posting any you find please :-) www.trainweb.org/railwest/railco/sdjr/signals.html

'Recycled' by the RAF :-)