neilw
now that's what I call a garden railway
Posts: 284
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Post by neilw on Mar 15, 2011 18:01:04 GMT
how are shunt signals illustrated on signal cabin diagrams?
Looking at some pictures they are marked only (ie no actual representation of indication), yet on others they are not even shown, whilst on others (like Harsig's Avatar) there appears to be a lamp to show the position. I guess all three could be right depending on era? Many thanks
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Oracle
In memoriam
RIP 2012
Writing is such sweet sorrow: like heck it is!
Posts: 3,234
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Post by Oracle on Mar 15, 2011 18:32:10 GMT
Interesting query! I am always interested in signalbox diagrams. The photo of a west London NR 'box that I have shows various shunt signals as black circles with red bars.
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Deleted
Deleted Member
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Post by Deleted on Mar 15, 2011 18:38:07 GMT
Two that I know of have either a red or green light on the diagram or have a red light go out to no light.
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Post by citysig on Mar 15, 2011 18:56:02 GMT
There doesn't seem to be a standard, although on more modern diagrams they are always shown.
From memory, Edgware Road cabin has the signals drawn on, and even has the centre bar of the signal illuminated red or green depending on the signal state (it's quite a simple bulb set-up that gives a nice result).
Hammersmith (Met) has the signals drawn in both danger and clear states, with one disc above the other. At danger there is no illumination, whilst when clear the upper (clear) drawing illuminates (white light only).
Harsig's avatar shows the indications in Baker Street's Met SCC. On the fixed-line diagram the shunt signals are drawn on, and above each is one red and one white light. Red illuminates at all times unless the signal is cleared, when the white light illuminates. However on the computer screens which are used by the operators, the shunt signals are shown as a white arrow when cleared.
Just a few of the many numerous ways in which they are indicated.
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Post by 21146 on Mar 15, 2011 19:12:26 GMT
Given that shunt signals are semi's there should always been some form of indication. Draw-up signals are effectively approach/speed-controlled auto's so do not have an indication since the Sig/Op cannot hold them at danger. Whitechapel cabin has them shown this way.
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Post by 21146 on Mar 15, 2011 19:18:09 GMT
Similarly X-signals are shown like draw-ups as being auto's, and they cannot (normally) be held at danger.
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Post by railtechnician on Mar 16, 2011 18:39:53 GMT
From memory Earl's Court control room has shunt signals illuminated red when 'ON' and no indication when 'OFF', this is the same standard as in IMRs.
Generally signals which are not controlled from a site but shown for reference or completeness are drawn in their normal state i.e. autos as green and semi autos as red.
There are of course different diagram standards and the biggest difference is perhaps the tracks which may normally be illuminated white for unoccupied and unlit for occupied on older diagrams but unlit for unoccupied and shown red for occupied on newer diagrams.
Of course the change was probably as a result of overheating bulbs gradually 'cooking' the old diagrams, there are many browned ones around especially in floodgate relay rooms.
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Post by 21146 on Mar 16, 2011 20:53:48 GMT
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Deleted
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Post by Deleted on Mar 17, 2011 4:24:05 GMT
From memory Earl's Court control room has shunt signals illuminated red when 'ON' and no indication when 'OFF', this is the same standard as in IMRs. Generally signals which are not controlled from a site but shown for reference or completeness are drawn in their normal state i.e. autos as green and semi autos as red. They are green for off. Some can't be seen from the angle they should be and some lamps aren't lit! |
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Post by railtechnician on Mar 17, 2011 7:02:32 GMT
From memory Earl's Court control room has shunt signals illuminated red when 'ON' and no indication when 'OFF', this is the same standard as in IMRs. Generally signals which are not controlled from a site but shown for reference or completeness are drawn in their normal state i.e. autos as green and semi autos as red. They are green for off. Some can't be seen from the angle they should be and some lamps aren't lit! Yes I remember now, they were green for 'OFF' on the old diagram panels (thyristor red/green circuit) but when the control room was given a spruce up with new diagram panels lots of things didn't line up exactly, shunt lampholders were one and the others were diverging route signals as I recall. I spent time trying to make adjustments as the new panels were fitted to give the best sighting but as I recall getting one thing properly aligned upset another so what is seen is a compromise. This was of course a result of hand tracing over the old diagram panels to create the new ones, an amount of error crept in. As for the lamps, we all (control room TOs) used to spend time replacing duff ones but the lampholders themselves are of a poor standard and don't make the best contact with the signal type wedge bulbs. Then of course Earl's Court diagram wiring is now more than 50 years old which doesn't help the situation. Telephone type PO No.2 bulbs and lampholders as found in some IMR diagrams such as Ealing Common, Acton East, Acton West etc are slightly larger and more robust. |
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