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Post by zcap on Apr 5, 2016 19:48:51 GMT
Hi all. I was on the Eastbound(Platform 1 I think?) Circle Line Platform at Aldgate earlier and noticed signal OB6 at danger, which was no suprise. I imagined its purpose would be that of a draw up signal and it would wait for the train to enter the platform and slow before clearing. It did do as expected but when it cleared, it cleared to a Yellow Aspect rather then a green, which confused me. This signal is a two aspect signal which implies that it can only display red and yellow aspects. Slightly further up the platform was signal OB300, the draw up signal for the Eastbound Starter Signal OB30, and I believe that OB300 could only show red and yellow too, but I am not too sure. Nontheless, OB300's function is obvious and is hinted at by its signal box code, but OB300 being able to only display a Red or Yellow aspect is less suprising. My questions are, is OB6 a draw up signal, and why is it numbered as OB6 rather then OB300a and have OB300 as OB300b, in a similar fashion to multiple home signals. If OB6 it is a draw up signal, why doesnt it have a green aspect? I know Circle line trains usually wait for District line trains to pass ahead of them but with at least two more signals and trainstops between OB6 and Minories Junction, surely the green aspect couldnt hurt. And finally is there else on the network where similar Red/Yellow signals are used? Thanks  |
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Post by revupminster on Apr 6, 2016 16:20:03 GMT
Draw up signals in my day were called permissive signals and were three aspect, red yellow and green as at whitechapel where I trained as a Relief Booking Clerk as you had to be q
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Deleted
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Post by Deleted on Apr 6, 2016 16:39:52 GMT
Some may be 3 aspect but will only show a green on a fault.
One example is A8400 at Cannon Street as the starter A840 is approached controlled it will never show a green and only shows a yellow or red.
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Post by revupminster on Apr 6, 2016 16:46:09 GMT
Draw up signals in my day were called permissive signals and were three aspect, red yellow and green as at whitechapel where I trained as a Relief Booking Clerk as you had to be qualify at one signal cabin.
As you say they work in conjunction with the station starter in this way.
Station starter Green....Draw Up signal Green, trainstop down ie no need for extra protection
Station starter Red......Draw up signal Red trainstop up ie a need for extra protection to prevent a collision ahead of the starter
Station starter Red......Draw up signal Red trainstop up train approaches Draw up signal displays Red and Yellow when the train enters the speed timing section.
If the train is too fast the Yellow aspect goes out and the Red remains on Trip stays up and train is tripped.
If the train is correct speed the Red goes out, Yellow remains and the trip goes down.
Is OB6 maybe a wrong road starter. It is along while since I have been there
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Deleted
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Post by Deleted on Apr 6, 2016 17:09:42 GMT
Some may be 3 aspect but will only show a green on a fault. One example is A8400 at Cannon Street as the starter A840 is approached controlled it will never show a green and only shows a yellow or red. Which is, of course, not to say that there aren't any draw up signals left which work in the standard way and show green when the associated signal is green, e.g. EH900 at Embankment. And then, of course, there are the ones where no green aspect is even fitted, such as OB300 which the OP mentioned and the new incarnations at Whitechapel. Draw up signals in my day were called permissive signals and were three aspect, red yellow and green as at whitechapel where I trained as a Relief Booking Clerk as you had to be qualify at one signal cabin. As you say they work in conjunction with the station starter in this way. Station starter Green....Draw Up signal Green, trainstop down ie no need for extra protection Station starter Red......Draw up signal Red trainstop up ie a need for extra protection to prevent a collision ahead of the starter Station starter Red......Draw up signal Red trainstop up train approaches Draw up signal displays Red and Yellow when the train enters the speed timing section. If the train is too fast the Yellow aspect goes out and the Red remains on Trip stays up and train is tripped. If the train is correct speed the Red goes out, Yellow remains and the trip goes down. Is OB6 maybe a wrong road starter. It is along while since I have been there The OP has described the operation of OB6 correctly, the wrong-road starter is OB20, unless I'm very much mistaken  |
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DWS
every second count's
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Post by DWS on Apr 6, 2016 18:04:51 GMT
Some may be 3 aspect but will only show a green on a fault. One example is A8400 at Cannon Street as the starter A840 is approached controlled it will never show a green and only shows a yellow or red. How can they show a green on a fault ? |
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Deleted
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Post by Deleted on Apr 6, 2016 18:11:21 GMT
have a look at the print for it
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Post by philthetube on Apr 6, 2016 18:23:53 GMT
If a draw up signal can only show a red or yellow aspect the signal ahead is almost certainly approach controlled and will never be green when the train passes the draw up, negating the need for a green aspect.
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North End
Beneath Newington Causeway
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Post by North End on Apr 6, 2016 19:39:06 GMT
If a draw up signal can only show a red or yellow aspect the signal ahead is almost certainly approach controlled and will never be green when the train passes the draw up, negating the need for a green aspect. There is/was definitely one place where there was a red/yellow draw-up in the rear of an approach-controlled starter, where with the train going slowly enough it was possible to see the draw-up displaying yellow with the starting signal displaying green. Can't remember where this is/was! |
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Tom
Administrator
Signalfel?
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Post by Tom on Apr 7, 2016 13:46:58 GMT
OB6 was originally a three aspect signal and dated from resignalling in 1988. In its original arrangement, it could show green if OB30 was clear.
As part of the S Stock Enabling works OB30 had to be relocated and OB300 was provided. Under the new arrangement, as OB6 cleared to authorise a train to OB300 which would always initially be at danger, the green aspect on OB6 became unnecessary and was removed.
There were other red/yellow draw up signals on the network; A2320 at Barbican and OP300 at Edgware Road are two I can think of.
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Tom
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Post by Tom on Apr 7, 2016 13:48:14 GMT
Some may be 3 aspect but will only show a green on a fault. One example is A8400 at Cannon Street as the starter A840 is approached controlled it will never show a green and only shows a yellow or red. It still didn't stop one rather well-paid contractor asking me how you'd go about testing the green aspect. I said it would be easy enough to functionally test but somewhat harder to do from a principles perspective! |
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Post by bassmike on Apr 7, 2016 15:24:19 GMT
If the green only shows on a fault they should take the bulb/led out.
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Post by zcap on Sept 13, 2016 19:21:27 GMT
Great! Excellent answers! Thanks for all the responses! (And sorry for my late response) 😊
One further question (maybe slightly in advance of the original topic), I heard a rumour recently that, OB300 was introduced to remove a set of trap points in advance of Minories junction. Not sure how true this is though.
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Deleted
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Post by Deleted on Sept 13, 2016 19:37:30 GMT
Great! Excellent answers! Thanks for all the responses! (And sorry for my late response) 😊 One further question (maybe slightly in advance of the original topic), I heard a rumour recently that, OB300 was introduced to remove a set of trap points in advance of Minories junction. Not sure how true this is though. As far as I'm aware there weren't any trap points in advance of (i.e. beyond/past/after) Minories Junction even in the last days of Aldgate cabin. There were trap points in rear of (i.e. on the approach to/before) Minories Junction just outside the Circle line platform (platform 1). It's actually a full trap road with buffer stops at the end. It's still there and I'm sure it's not going anywhere. |
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Post by zcap on Sept 13, 2016 20:02:21 GMT
As far as I'm aware there weren't any trap points in advance of (i.e. beyond/past/after) Minories Junction even in the last days of Aldgate cabin. There were trap points in rear of (i.e. on the approach to/before) Minories Junction just outside the Circle line platform (platform 1). It's actually a full trap road with buffer stops at the end. It's still there and I'm sure it's not going anywhere. Yes of course, I meant in advance of OB6 and indeed OB30 (in rear of minories junction. Doh!)! Indeed I have observed the current trap road. A nice precaution. I was wondering though the rumour was a bit off, there doesnt look to be any space beyond the Minories end of Platform 1 for another set of trap points. Thanks for the quick response! |
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Post by Harsig on Sept 13, 2016 20:38:13 GMT
OB300 was installed because OB30 had to be moved closer to the points in order for S7 trains to fit into the platform.
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