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| Semaphore Signal Diagram Question: 23/04/2010 at 17:14 #1162 | |
Danny252
1461 posts |
On the far left of the linked diagram (Carlisle No13), lever #1B shows 2 arm pictures - a solid home-shape and an outline distant-shape. Lever 23 is similar, but both arms are home-shaped. I've seen this before, but I've yet to work out 2 things: 1. The arms are co-situated with another SB's arms. However, does this 2-arm-thingy indicate that: The arm is solely worked by box 13? The arm is solely worked by box 12? That both must pull a lever for it to pull off? (I don't know if this working acutally exists, I only have a faint inkling of it being mentioned in the back of my head). 2. Does the fact lever 1B shows 2 different shapes matter? Does this indicate, say, the distant for #13 being interlocked with the starter for #12? Link: http://www.signalbox.org/diagrams.php?id=257 Log in to reply |
| Semaphore Signal Diagram Question: 23/04/2010 at 17:14 #8730 | |
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Danny252
1461 posts |
On the far left of the linked diagram (Carlisle No13), lever #1B shows 2 arm pictures - a solid home-shape and an outline distant-shape. Lever 23 is similar, but both arms are home-shaped. I've seen this before, but I've yet to work out 2 things: 1. The arms are co-situated with another SB's arms. However, does this 2-arm-thingy indicate that: The arm is solely worked by box 13? The arm is solely worked by box 12? That both must pull a lever for it to pull off? (I don't know if this working acutally exists, I only have a faint inkling of it being mentioned in the back of my head). 2. Does the fact lever 1B shows 2 different shapes matter? Does this indicate, say, the distant for #13 being interlocked with the starter for #12? Link: http://www.signalbox.org/diagrams.php?id=257 Log in to reply |
| Semaphore Signal Diagram Question: 23/04/2010 at 17:33 #8732 | |
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Late Turn
699 posts 
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Firstly, I suspect you're referring to 1B, rather than 18 (which is the miniature arm reading from the Down Home to the Down Reception) - presumably lever 1 works both 1B (outer distant) and 1A (inner distant - allowing the colour light to step up to green). The 'blacked out signal' indicates the presence of a slot (i.e. that the box in rear - Carlisle No. 12 - has some control over the working of that signal). In this case, as I think you're suggesting at the end of your post, 1B will be slotted (backslotted? Not sure of the technicalities) with No. 12's section signal (the colour light) - to ensure that 1B can't be cleared with No. 12's section signal still at Danger, with hopefully obvious potential for serious misinformation to the Driver. There'll also be some slotting with the arm on the same post, but that's presumably not shown. Note also 23 signal, which No. 12 also has (presumably direct, in this case) control over. I don't know whether that's some sort of wrong-direction move over the Down Reception, perhaps to attach a loco onto a train standing on that road. Hope that helps - I can try to explain it another way if the above (understandably!) just confuses. Tom Log in to reply |
| Semaphore Signal Diagram Question: 23/04/2010 at 18:44 #8734 | |
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Danny252
1461 posts |
Tom Nicholson said:Firstly, I suspect you're referring to 1B, rather than 18 (which is the miniature arm reading from the Down Home to the Down Reception) Indeed I did! I've corrected the first post. Quote: I wonder if the other arm is the actual section arm on that post - with the other "home arm" there being merely to illustrate the slotting? It wouldn't make much sense, in my experience, to have 2 home arms on the same post (other than co-acting, and possibly some location-specific indication in severely space-limited areas?) Quote: Note also 23 signal, which No. 12 also has (presumably direct, in this case) control over. I don't know whether that's some sort of wrong-direction move over the Down Reception, perhaps to attach a loco onto a train standing on that road.Possible - I think a similar reversible-direction working is used between the Bewdley boxes on the SVR for the rock siding (with both having a lever to determine the direction of working). Log in to reply |
| Semaphore Signal Diagram Question: 23/04/2010 at 19:07 #8735 | |
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Late Turn
699 posts
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Yes, sorry, the 'black' arm isn't physically there - it just indicates the presence of a slot. The stop signal indicated above is (or was) there 'on the ground' (but isn't the section signal - that's the colour light in advance). I don't know the arrangement at Bewdley too thoroughly, but I suspect that - as it's a passenger line - it's worked by acceptance or direction lever rather than slotting. The concept's similar, but only - I believe - releases the signal at the box in rear, rather than controlling it cooperatively. Tom Log in to reply |
| Semaphore Signal Diagram Question: 23/04/2010 at 20:55 #8746 | |
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Adrian the Rock
111 posts |
In general, black arms are ones controlled by other boxes, white ones by Carlisle No 13. A black arm shown at 45 degrees does indeed indicate the 'white' arm it coincides with is slotted from another box, and distant 1B will indeed have been backslotted with Carlisle No 12's colour-light section signal. This colour-light also functions as No 13's inner distant 1A. When No 12 clears his lever, the signal would change from red to yellow; when No 13 then clears his distant (lever 1 - the designations 1A and 1B indicate they are both worked from the same lever) it goes green. The signal is not a 4-aspect; the bottom yellow is marked as an auxiliary aspect, ie it lights up only if the upper yellow's lamp has failed. The 'outer' end of the outer distant arm 1B is actually also coloured in black (this may not be immediately apparent on this particular diagram, yet is recognisable once you know to look for it) which signifies that the arm is motor operated. The backslotting would have been arranged electrically, probably by taking the circuit that energises the 1B signal motor through a contact on the green aspect proving relay on the colour-light section signal. No 23 is a stop arm which is also slotted with another box - again presumably No 13 - so the arm will only clear when both boxes have pulled their respective levers. Log in to reply |
| Semaphore Signal Diagram Question: 25/04/2010 at 13:47 #8755 | |
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kbarber
1742 posts |
Without knowing the detailed layout at No. 12 Box it's also possible that the Stop arm co-located with 1B is controlled from yet a third 'box. In that case 1B is not only No. 13's outer distant, it's also No. 12's distant (or inner distant) hence is directly dual-controlled by both boxes as well as slotted by the stop arm above it (using electrical means to achieve the complex slotting & backslotting required. I emphasise that's speculation unless someone can turn up a diagram of Carlisle No. 12. But it was once normal practice and I was fortunate enough to see it in operation at Finchley Road (Midland) in early 1978, with Finchley's inner distants (on both Main and Suburban lines) beneath West Hampstead's starters and two outer distants for each line, beneath West Hampstead's homes and Cricklewood's starters (as if 1B in the Carlisle diagram was itself duplicated). (A few years earlier there had been a 'box at Watling Street, between Cricklewood & West Hampstead, but I have no idea what the arrangements were in those days; somehow I suspect there hadn't been three outer distants though - that really would have tested drivers' roadlearning skills!) Log in to reply |