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Post by Deleted on Sept 12, 2005 7:41:44 GMT
Whilst reading through some threads on u.t.l. I came across a list of signal box codes for the Northern Line, and the list stated that London Bridge's code was P (it had a trailing crossover). The list then said that it was changed to X during the rebuild of the Northern station, and that the only aspect of the site that remains controllable are the station starters, X643 and X638 - the remainder of the signals in the area being FNX signals.
Why were things done this way? Surely it would have been better to renumber the necessary signals as P (such as the starters and some of the FNX homes), yet place them into the auto series for the Bank branch (similar to Totteridge and the ground frame).
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Post by Deleted on Sept 12, 2005 23:59:36 GMT
There's a lot of historical reasons why signals are numbered as they are, but I don't think 'P' (on its' own) is now an acceptable cabin code, as signal with 'PxX' prefixes designate an X signal protecting an engineering possession. (On the Northern line, this would be PNX).
As I've never worked on the Northern, I can't answer with any more information!
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Post by Deleted on Sept 13, 2005 8:41:21 GMT
The entire Northern Line is a bit wonky in that respect - it has single-letter signalbox codes on the Morden, CX, Bank and Edgware branches. The High Barnet branch is the only one that has two-letter codes.
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Post by q8 on Sept 13, 2005 9:31:40 GMT
Well al that will change 'WHEN' the niw signalling is installed I assume.
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Tom
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Post by Tom on Sept 13, 2005 10:37:34 GMT
The High Barnet branch is the only one that has two-letter codes. Err... cough cough... Edgware and Colindale? X refers to an Auto signal which must be treated as a controlled signal. The whole site is now an auto area. |
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Post by Deleted on Sept 13, 2005 10:45:50 GMT
The High Barnet branch is the only one that has two-letter codes. Err... cough cough... Edgware and Colindale? Heh, whoops  X refers to an Auto signal which must be treated as a controlled signal. The whole site is now an auto area. Certainly - I don't dispute that. I'm just curious as to why a pair of directly controllable signals are simply called "X" (a la Barons Court and Hounslow West), instead of something like "PX" (a la the Uxbridge branch - MUX743 comes to mind). AlanL did say that "PNX" is used when breaking auto signals that are near a possession - is that why "PX" was not used? |
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Tom
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Post by Tom on Sept 13, 2005 10:55:37 GMT
Check the numbering of your directly controllable X signals - they're from the Auto sequence...  (Have you got a link to the utl post BTW?) |
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Post by Deleted on Sept 13, 2005 12:11:29 GMT
Check the numbering of your directly controllable X signals - they're from the Auto sequence... Indeed they are! I typed the signal numbers down and never even noticed that they are indeed in the auto sequence. That's one oddity dismissed, how about the other (namely, why X instead of PX or just P)? (Have you got a link to the utl post BTW?) . |
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Tom
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Post by Tom on Sept 13, 2005 12:58:54 GMT
Ah, by one Mr Splett. I think what he's getting at is that the signals can be maintained at danger, but are not strictly controlled. X341 @ Waterloo (S/B Bakerloo) is similar.
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Post by Deleted on Sept 13, 2005 13:28:09 GMT
Ah, by one Mr Splett. I think what he's getting at is that the signals can be maintained at danger, but are not strictly controlled. X341 @ Waterloo (S/B Bakerloo) is similar. Indeed. I just can't seem to understand what the rules are for assigning the single letter X to a signal - I don't dispute that it is usually assigned to autos that must be treated as controlled signals, but the type of control exercised over the signal is muddying the issue for me. |
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Colin
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Post by Colin on Sept 13, 2005 13:30:34 GMT
Well I dunno bout the Northern - But everywhere else, an 'X' signal is basically an auto.
The reason they are made 'X' signals is: a train operator must treat them as a semi automatic signal when they remain at danger.
That is they cannot pass that signal remaining at danger without permission from the signal operator, whereas, providing procedure is followed correctly, an automatic signal (with no 'X' in the number) can be passed at danger on the train operator's own authority.
I'd imagine the ones being talked about are approach controlled?
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Post by q8 on Sept 13, 2005 16:11:34 GMT
When we were trained we were told that an 'X' signal was ALWAYS the last auto before a controlled area. This turned out to be another untruth.
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Post by Harsig on Sept 13, 2005 16:27:35 GMT
The entire Northern Line is a bit wonky in that respect - it has single-letter signalbox codes on the Morden, CX, Bank and Edgware branches. The High Barnet branch is the only one that has two-letter codes. Interestingly I've just acquired a reasonably comprehensive list of Northern Line Cabin codes and how they developed. Starting with Charing Cross, Euston & Hampstead, initially single letter codes were used throughout and were as follows B Charing Cross (Later changed to C) D Mornington Crescent E Camden Town F Hampstead G Golders Green H Highgate (now Archway) Turning to the City & South London, this acquired single letter codes during th resignalling in 1919. By this time it was already planned to amalgamate the two lines and so the sequence followed on from the CCE&H and was as follows J Euston K Angel L Old Street M Moorgate P London Bridge U Stockwell T Clapham Common The extensions built as part of the amalgamation of the two lines added the following to the list A Kennington (Later changed to B) W Tooting Broadway Y Morden Note: At this time Automatic signals were denoted by the letter S and therefore A was a valid cabin code. The Edgware extension resulted in a new series of cabin codes, these being two letters, the first such examples on deep level tube lines. The following were provided. AA Brent AB Hendon Central AC Colindale AE Edgware |
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Post by Deleted on Sept 13, 2005 17:04:00 GMT
Interestingly I've just acquired a reasonably comprehensive list of Northern Line Cabin codes and how they developed. Sounds like something I'd do ;D Starting with Charing Cross, Euston & Hampstead, initially single letter codes were used throughout and were as follows B Charing Cross (Later changed to C) D Mornington Crescent E Camden Town F Hampstead G Golders Green H Highgate (now Archway) Turning to the City & South London, this acquired single letter codes during th resignalling in 1919. By this time it was already planned to amalgamate the two lines and so the sequence followed on from the CCE&H and was as follows J Euston K Angel L Old Street M Moorgate P London Bridge U Stockwell T Clapham Common Why U instead of R for Stockwell, and S instead of T for Clapham Common? The extensions built as part of the amalgamation of the two lines added the following to the list A Kennington (Later changed to B) W Tooting Broadway Y Morden Note: At this time Automatic signals were denoted by the letter S and therefore A was a valid cabin code. The Edgware extension resulted in a new series of cabin codes, these being two letters, the first such examples on deep level tube lines. The following were provided. AA Brent AB Hendon Central AC Colindale AE Edgware What was wrong with AD? |
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Post by Harsig on Sept 13, 2005 17:52:47 GMT
Why U instead of R for Stockwell, and S instead of T for Clapham Common? At the time Automatic signals were denoted by S e.g. S53 and therefore S could not be used as a cabin code. Likewise R was and still is used for repeaters and so also cannot be used as a cabin code. Most likely set aside for possible use at Burnt Oak |
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Post by Deleted on Sept 13, 2005 18:38:31 GMT
Why U instead of R for Stockwell, and S instead of T for Clapham Common? At the time Automatic signals were denoted by S e.g. S53 and therefore S could not be used as a cabin code. Likewise R was and still is used for repeaters and so also cannot be used as a cabin code. Ah, right! I had forgotten that S was used for autos on the Northern. Still though, why U for Stockwell and T for Clapham Common, instead of the other way around? Most likely set aside for possible use at Burnt Oak Fair enough. |
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