S signals

[JR 15secs]

Don't know if this one's been asked before but as I understand it the Northern line still has S signals can anyone tell me where they are and how many?

[JR 15secs]

Well seem no one answered I've done it myself details as follows: total S signals left is 59 of which 47 are actual signals and 12 are repeaters further broken down as follows Camden Twn-Kings X SB 4 sigals 2 repeaters, Euston (C)-Camden Twn NB 1 signals, Sth Wimbledon-Clapham Sth NB 20 signals 5 repeaters, Clapham Com-Colliers Wd SB 22 signals and 5 repeaters. I now intend to see how many there were over the previous years, any help would be grateful.

[Deleted]

sorry but i dont know the northen line so i cannot help

[Deleted]

Wouldn't a repeater be technically an R signal?

My vast (sic) catalogue of S signals

tinyurl.com/2k7x38


tinyurl.com/37wmpf



What time frame are you looking at? I'd guess that without any major re-signaling the S signals wouldn't be re-numbered(lettered).

With ATO due fairly soon on the Northern Line, these signals will no doubt be going.

[Deleted]

Charing X branch south bound approach to Kennington, you have cluster BX51A, and also RFNX51B B2.
G=Golders, AC=Colindale, AE=Edgware, Y=Morden, U=Stockwell, C=Charing Cross, E=Camden Town, NN=Archway, NQ=Finchley Central, NU=High Barnet...

[Deleted]

what exactly do S signals do that other signals don't?

[Deleted]

At least on the Northern, S signals used to denote Automatic Signals...

know at least a few of years ago, there were still some in the Colliers Wood area

[Deleted]

so what now denotes them?

there can't be only 59 automatics on the Northern surely?

[CSLR]

rob said:

what exactly do S signals do that other signals don't?

'S' ('RS' for repeaters) was the a prefix given when automatic signals where introduced. They have been slowly disappearing for decades during signalling alterations having been replaced by the prefix 'A' for automatic.
'S' and 'A' are therefore the same.

[Deleted]

Auto Signals are now prefixed with an A, thus A604, etc...

[Deleted]

The reason why the Northern uses S signals is because the A prefix is used for IMR 'AC' and IMR 'AE' at Colindale and Edgware, respectively.

[Tom]

theonekea said:

The reason why the Northern uses S signals is because the A prefix is used for IMR 'AC' and IMR 'AE' at Colindale and Edgware, respectively.

I doubt it. The second letter in the code at those sites will indicate that the signals are controlled and therefore no misunderstanding should occur.

[Deleted]

tom said:

theonekea said:

The reason why the Northern uses S signals is because the A prefix is used for IMR 'AC' and IMR 'AE' at Colindale and Edgware, respectively.

I doubt it. The second letter in the code at those sites will indicate that the signals are controlled and therefore no misunderstanding should occur.

Hmmmm - I guess that A for Auto was a later development of the Underground then. I wonder if CSLR knows why his namesake chose S for signal as opposed to A for auto.

[CSLR]

theonekea said:

I guess that A for Auto was a later development of the Underground then. I wonder if CSLR knows why his namesake chose S for signal as opposed to A for auto.

Although it seems perfectly logical with hindsight, I do not think that it occurred to anyone to use 'A' for auto at that time. When the C&SLR was joined onto the CCE&H it took into account that line's existing codes:-

B - Strand
E - Camden Town & Mornington Crescent
F - Hampstead
G - Golders Green
H - Highgate

Kennington, which would be common to both lines was allocated the letter 'A' making it unavailable for automatic signals on the line.* The C&SLR cabins were given letters that fitted in with the CCE&H codes. It was roughly sequential except for Stockwell, which should logically have adopted the prefix 'S' - both as a memorable identification and to fit into the alphabetical sequence - but had to be given a different code because of the use of that letter on automatic signals.
When automatic signalling was introduced throughout the line, the codes were thus:-

AA - Brent (Edgware extn)
AB - Hendon Central (Edgware extn)
AC - Colindale (Edgware extn)
AE - Edgware (Edgware extn)
A - Kennington (CCE&H - C&SLR)
B - Strand (CCE&H)
E - Camden Town & Mornington Crescent (CCE&H - CSLR)
F - Hampstead (CCE&H)
G - Golders Green (CCE&H)
H - Highgate (CCE&H)
J – Euston (C&SLR)
K – Angel (C&SLR)
L – Old Street (C&SLR)
M – Moorgate Street (C&SLR)
P – London Bridge (C&SLR)
Q – Elephant & Castle (C&SLR)
U – Stockwell (C&SLR)
T – Clapham Common (C&SLR)
W - Tooting Broadway (C&SLR)
Y - Morden (C&SLR)

S - Automatic signal


* With the closure of the Strand cabin, Kennington was changed to 'B' in 1937, thus releasing 'A' for use on automatic signals.




_{Edit - added additional notes}

[Deleted]

Interesting info - I suppose it was the original provision of codes on the CCE&HR that led to the use of A for Kennington. It makes you wonder if the same choice would have been made if it was known that the lines would soon be linked together.

[Deleted]

Thanks for that CSLR - I'll add them to my notes...

[Deleted]

S signals are automatic but as they had a special relay they kept the S until the relays were replaced when they became A signals. There were still a couple around when I was a guard as recently as 1999. This was the story given to us during training and I don't know if any are left.

[Deleted]

a special relay you sure ? automatic signals do not have special relays

[Tom]

That sounds like the standard answer from Ashfield House given during OPT.
I have done some research into this and there doesn't seem to be any basis for this explanation, though if anyone with some knowledge of Northern Line signalling knows better please speak up!

[mandgc]

A descision was made early on to identify purely automatic signals as 'S' on the Underground group (and why not?)and this made all letters except R and S available for Signal Box Codes. 'A' was used for some Edgware Line signal boxes when they opened. Later it was decided to re-letter these signals as 'A' though the changeover has been delayed by possible difficulties in changing Signalling records.

Looking through some cuttings I see that the Metropolitan Railway started to show their Automatic Signals as 'A' a year after the Edgware line was opened and these applied to the new 3 aspect Colour Light signals between Harrow and Rickmansworth. These automatic signals were also shown as 'A' on the Watford, Uxbridge,and Wembley to Harrrow and Stanmore line new signals. Before this 2 Aspect Colour Light Automatic Signals on the Circle and Widened lines and also during resignalling at Edgware Road in 1926 were designated as 'S'.
'S' numberplates also applied to the 2 Aspect Upper Quadrant Auto signals between Finchley Road and Wembley Park when the line was quadrupled and these ,I think, remained until the line was resignalled for the Bakerloo extension to Stanmore in 1939.

[JR 15secs]

Thanks for all the answers the Bakerloo lost S signals 1930s/40s the Central lost them 1940s with the other parts of the Northern mostly 1970s during resignalling of auto areas.

[motormanmet]

Just a few thoughts on topics discussed...

As said, the introduction of automatic signalling on the District Rly from 1905-onwards saw 'S' denote an automatic SIGNAL. All lines from then on used 'S', however this included the Harrow to Watford and Ricky extensions of the mid-20s. 'A' was the cabin code for Watford until it was changed to 'JL' (late-40s/early-50s, date not to hand). Autos mostly remained 'S' until the 4-tracking of 1961-2.

First use of 'A' was almost certainly the Uxbridge resignalling of 1930. Thereafter, all new schemes used 'A' and existing lines began to slowly be re-prefixed. Many central parts of the Yerkes tubes were changed to 'A' during the 30s, necessitating changing the cabins using 'A' as a code to something else (such as Kennington, Hammersmith Pic, Queens Pk, Liv St central, Baker St met). Interestingly, a journey on the Met main line from Aldgate to Watford in the early 40s would show many faults with the prefix system: 'A' was in use for auto signals from Baker st - Wembley and for Watford, 'B'-'H' on the Circle line were repeated from Harrow northwards. It wasn't until the early 1960s that clashing codes were eliminated.

Interestingly, the Metropolitan pre-LT denoted repeaters for auto-signals 'RS'.

I have also heard the story of 'S' signals being retained on parts of the northern to denote that signal has a different (older?) type of relay to signal engineers - not sure how much truth is in that, but it could explain why these were never changed and others in proximity were chaned to 'A'. Not a special relay as such, just a different one.

Oddly enough, when king levers were introduced from the 20s to make semi's work automatically, the illuminated indicators to show this to drivers displayed 'A' for automatic, even if the signal was prefixed 'S' on the plate! This may be connected with the fact that from the same time, the District and Met adopted new starting arrangements for hand-worked stock - the guard would short out twin copper wires suspended above his position at the rear end of the platform to display an illuminated 'S' for start below the starting signal. This would possibly necessitate using illuminated 'A's for semi-auto signals instead. This may have even prompted the adoption of 'A' for automatic signal prefixes - the Uxbridge branch being the first user of 'A' for autos had the 'S' starting displays for T-stock trains provided during the 1930 resignalling.