Curious about manoeuvers at Earl's Court & High St

Excellent - a much appreciated and comprehensive explanation, Colin. All the mysteries are being cleared up one by one. I remember a time when I didn't even understand how two trains could leave ECT for Wimbledon simultaneously!

Just to clarify re "EV" & "169" - I had (probably mistakenly) imagined that the codes which appear on signal room photos were common reference terms to identify areas - not that I'd expect anyone to carry all the codes in their heads.

For instance in this image: www.anorakheaven.com/photos/ect_cr33.jpg

169 is written next to the "bays" on one side of Triangle.
EV is the stretch of track seen just after signal ED23. I presumed those codes must be documented on track maps/in books elsewhere but I've never found out where! "Answers on a postcode...".

Incidentally I note ED23 has three routes - route 1 = into pfm3, route 2 = into pfm4, route 3 = info pfm2. I can't imagine how that the route indicator shows this clearly on the signal head (not that I "need" to know - just curious!)

Thanks as always for the enlightenment - hope it's useful info for other curious folk too.

karona

Apologies for the OT, but the pic of WD43 et al, is there a WD40 somewhere?

Unfortunately, there isn't!!
There are WD40A, WD40B and WD40C though, (between Barons Court and Hammersmith)

169 is the lever number for the lever in IMR 'ED' that controls the three outlet shunt signals from the three sidings to the northbound District. The same number is shared by all three signals because this particular frame uses route lever principles in this area, and when 169's is rotated reverse, the correct shunt signal drops based upon the lie of the points in the route. I'm not certain how this is done in the circuitry, but at a minimum a series of electrical track locks and point blade ground locks (possibly including FPLs?) must be proved in each set of points and track circuits up to the limit of control for 169's in order for any of the three signals to clear. railtechnician would probably be able to explain it far better than I ever could.

"EV" is the name of the particular track circuit in the area of the trailing crossover north of the points leading to the sidings. All track circuits on traditionally-signalled lines have a two or three letter code that uniquely identifies them within the controlled area supported by the IMR/SER (in this case, IMR 'ED'). These track circuit names are probably tracked (no pun) in the same set of documents as the master plans for the entire layout; BAET would know about that.

Yep 169A, 169B and 169C are all on the same lever so there is just one feed to clear the appropriate stick. This feed is routed to the appropriate shunt signal valve according to the lie of the points. Points are normal or reverse and their indicating relays similarly operate normal or reverse in correspondence. The required route is basically obtained by seriesing the necessary contacts of these and other relays (e.g. fouling track relays proved up) to select the signal. This is known as 'signal selection' and for 169 lever there are three selections from the same feed each of which mutually excludes the other too.

The track circuit allocations are shown on the signalling scale plans as well as on the signal operator diagrams and are of course shown in the various signal strip prints and bookwirings too.

To further clarify this bit....

Drivers do have to learn cabin codes of areas so that they know which signaller they are to deal with if communication is required, but there is no requirement to know all individual signal numbers (though I could tell you exactly where A681 is, or EC1 or ED23 or FF3, to name a few - some do stick in the memory for various reasons). Had you included the cabin code EC with the 169 reference, I'd have more than likely realised what you were referring to but when it comes to sidings, they are individually numbered under a different system to distinguish them.

As for the EV track circuit, that is definitely something us drivers have no need to know. I did suspect that was what you were referring to but I have no way of checking without going onto a work PC and pulling up the relevant line diagram. At the time I saw your post and typed out the original reply, I was at home and so it was just far easier to dismiss it and use a far easier a explanation - besides, most people viewing this forum will never have access to such information so it benefits us all to keep questions & answers as easy to understand as possible.

For purposes of identification a line is determined to be east and west regardless of its actual heading. As you have spotted westbound takes even numbers and eastbound odd numbers, the is the basic setup for a fully auto signalled line with signals beginning at one end i.e. A1 (eastbound) and A2 (westbound) and running in order to the other end say A399 and A400 but not necessarily continuous numbering as gaps are left for possible future alterations to track layour etc.

The signal number is the basis of the track numbering thus the track beyond the replacing track for signal A123 might be expected to be A123a and the following tracks say A123b, A123c and perhaps A123d as the replacing track of the signal ahead, A125 and so on. The tracks beyond beginning A125a etc.

However, where there are points the signals are semi-automatic and thus have to be controlled by a signal operator or other control. Signals in controlled areas take their identity from the 'cabin' or 'imr' which controls the area and tracks are lettered. Basically tracks run from A-Z through the site for a single track site but again there may be gaps. For a standard double track site the designations will generally be in alphabetical order on each road starting with A on one road and say L on the other although it simply depends on how many tracks are in the controlled area. For a complex site tracks may be AA-AZ on one road and BA-BZ on another and in four tracked areas the other two roads will use CA-CZ and DA-DZ. F,G & H followed by a second letter are usually allocated to sidings but it is not always the case.

There are no hard and fast rules but there are basic principles to determining the various designations in any layout. In a controlled area the layout of the levers on the frame determines the numbers of the signals but the layout of the levers depends upon the layout of the track and the complexity or otherwise of the locking. Basically the track plan would be first followed by the signal to use the layout according to operating department wishes. Such wishes change over time and involve partial or sometimes full resignalling which obscures the original designation scheme somewhat as does the fitting of additional signals to mitigate hazards and events which were unforeseen in the original signalling design.

When one works/has worked on the railway for a few years things are not too difficult to read but I do appreciate the difficulty of trying to do it at a distance without clear rules which I cannot give but perhaps Tom may explain further as he is a Principles man!