Tigger Posted October 30, 2011 Share Posted October 30, 2011 Can some one tell me if Theatre Indicators are on all the time or just when Signal is set to off? Link to post Share on other sites More sharing options...
RMweb Gold Colin_McLeod Posted October 30, 2011 RMweb Gold Share Posted October 30, 2011 Just when it is off. At all other timese there is no route available to anywhere. Link to post Share on other sites More sharing options...
RMweb Gold The Stationmaster Posted October 30, 2011 RMweb Gold Share Posted October 30, 2011 They only illuminate when the signal is showing a proceed aspect be it a main aspect or a sub). (I'm not quite sure what would happen if they were illuminated with a signal at danger as apart from being dangerously misleading what route would they show if there wasn't one available due to flank moves etc? - the mind boggles) Link to post Share on other sites More sharing options...
Tigger Posted October 30, 2011 Author Share Posted October 30, 2011 Thnks for your help guys Link to post Share on other sites More sharing options...
royaloak Posted October 30, 2011 Share Posted October 30, 2011 The theatre box (or route indicator) will light first as the route is proved, the signal will clear a second or 2 later. Link to post Share on other sites More sharing options...
Tigger Posted October 30, 2011 Author Share Posted October 30, 2011 The theatre box (or route indicator) will light first as the route is proved, the signal will clear a second or 2 later. does that work in reverse. ie the signal will go to ON and then the theatre box will go out? Link to post Share on other sites More sharing options...
ForestPines Posted October 30, 2011 Share Posted October 30, 2011 In my experience, the change back to "on" happens instantly: the proceed lamps go out, the route indicator goes out, and the red lights, all at the same time. A signalling expert might correct me here, but as I understand it, the delay when the signal clears is because the route indicator has to be proved working before the main aspect clears. If this didn't happen and the indicator was defective, the signal could fail wrong-side by appearing to show clear for a higher-speed route than the one set. Also - someone please correct me if I'm wrong - in a circuit with now-old-fashioned filament lamps in the indicator and relays in the cabinet, the current draw with 60% of the lamps lit will be enough to operate the proving relay, so a signal with a feather should still clear with only 3 out of 5 lamps working. Link to post Share on other sites More sharing options...
Edwin_m Posted October 30, 2011 Share Posted October 30, 2011 To my recollection ForestPines is right. With a solid state interlocking the delay from the route indicator to the signal is nearly one second, due to the way the SSI checks each trackside device in turn, but with relays it will be quicker. If the route indicator is working and there is a fault on the proving circuit then it is possible, but rare, for the route indicator to light with the signal at danger. This would only happen when the relevant route is in fact fully set and locked. Theatre proving must be more complicated than a simple three out of five, as there are plenty of combinations where 40% or fewer of the lights have failed and the indicator appears to be displaying a valid indication but it is the wrong one. For example an "8" might be seen as a "5". Link to post Share on other sites More sharing options...
meld Posted October 30, 2011 Share Posted October 30, 2011 Hi All, You can get a route shown on the main aspect of the signal and not have a theatre indicator lit too BTW .... the route shown via the main aspect would be the main route and have a line speed of 30 mph or greater as well ... this might help a bit .... http://www.rgsonline.co.uk/Rule_Book/Rule%20Book%20Modules/S%20-%20Signals/GERT8000-S1%20Iss%201.pdf Mike Link to post Share on other sites More sharing options...
Grovenor Posted October 30, 2011 Share Posted October 30, 2011 Route indicator proving has been done in many ways, often if all the routes were the same speed as may be the case approaching a terminus there may be no proving at all, but if one platform was significantly shorter, eg a bay then the indication may be proved for just that one. Where different speeds existed the proving may only cover specific lamps where the omission could lead to the route being confused with a higher speed one. This sort of thing was only needed where the bulbs were wired in parallel, which was the most common arrangement, at least in UK. The alternative was to wire in series, then one failed lamp took out the whole indication and no confusion was possible, in this type the lamp proving relay was also simple as the current was always the same. This type of indicator had special transformers with tappings to suit the number of lamps in series for each indication. Regards Keith Link to post Share on other sites More sharing options...
Guest jim s-w Posted October 30, 2011 Share Posted October 30, 2011 I haven't got my head round it yet but new streets searchlight signals used route indicators for shunt moves. Only actual departures were controlled by the main aspect. I think the situation at new street may have been unique Cheers Jim Link to post Share on other sites More sharing options...
royaloak Posted October 30, 2011 Share Posted October 30, 2011 ForestPines has it spot on. Link to post Share on other sites More sharing options...
RMweb Gold beast66606 Posted October 30, 2011 RMweb Gold Share Posted October 30, 2011 To my recollection ForestPines is right. With a solid state interlocking the delay from the route indicator to the signal is nearly one second, due to the way the SSI checks each trackside device in turn, but with relays it will be quicker. If the route indicator is working and there is a fault on the proving circuit then it is possible, but rare, for the route indicator to light with the signal at danger. This would only happen when the relevant route is in fact fully set and locked. Theatre proving must be more complicated than a simple three out of five, as there are plenty of combinations where 40% or fewer of the lights have failed and the indicator appears to be displaying a valid indication but it is the wrong one. For example an "8" might be seen as a "5". SSI checks in cycles, if the processor is not free to check the theatre is lit the one second you mention can be a lot longer, I've seen over 30 seconds for a "feather", from feather lit to aspect stepping up. Link to post Share on other sites More sharing options...
Edwin_m Posted October 31, 2011 Share Posted October 31, 2011 Having known and worked with most of the SSI development team I'd say that is one seriously sick SSI. Link to post Share on other sites More sharing options...
Absolute Aspects Posted October 31, 2011 Share Posted October 31, 2011 The theatre box (or route indicator) will light first as the route is proved, the signal will clear a second or 2 later. I had it once where I was coasting up to a red at Guildford and the theater box came off, the signal stayed at Red and then the theater box then went back out. Points had decided to fail up ahead... Link to post Share on other sites More sharing options...
RMweb Gold beast66606 Posted October 31, 2011 RMweb Gold Share Posted October 31, 2011 Having known and worked with most of the SSI development team I'd say that is one seriously sick SSI. Or busy ... Link to post Share on other sites More sharing options...
Talltim Posted October 31, 2011 Share Posted October 31, 2011 Very interesting thread. You don't realise how much thought goes into the failsafes on railways until you read something like this Link to post Share on other sites More sharing options...
RMweb Gold The Stationmaster Posted October 31, 2011 RMweb Gold Share Posted October 31, 2011 Or busy ... :lol: But there is no doubt at all that you can get noticeable delays between the route indicator illuminating and the signal clearing and people who have designed and tested SSI installations will confirm that to be the case. Alas a quick browse through the SSI overview manual last night failed to find any information on this aspect of their workings. Link to post Share on other sites More sharing options...
LNERGE Posted October 31, 2011 Share Posted October 31, 2011 Another feature of some route indicators is they can show front and back. Link to post Share on other sites More sharing options...
royaloak Posted October 31, 2011 Share Posted October 31, 2011 I had it once where I was coasting up to a red at Guildford and the theater box came off, the signal stayed at Red and then the theater box then went back out. Points had decided to fail up ahead... The Theatre box wont clear unless the route is set and locked, the signal wont clear unless the route is set, locked and the theatre box is proved. Sounds like a 3185 is in order for that one. Link to post Share on other sites More sharing options...
Tigger Posted October 31, 2011 Author Share Posted October 31, 2011 Phew and I thought it was a simple question Thanks for all the info Link to post Share on other sites More sharing options...
RMweb Gold TheSignalEngineer Posted October 31, 2011 RMweb Gold Share Posted October 31, 2011 I haven't got my head round it yet but new streets searchlight signals used route indicators for shunt moves. Only actual departures were controlled by the main aspect. I think the situation at new street may have been unique Cheers Jim New Street searchlights originally had theatres for signals where there was more than one destination. There were later replaced by stencil indicators after a number of misreading incidents. Shunt moves had subsidiary 'Cats eyes' with no indication of route for right direction moves and an indication for wrong direction moves e.g. up to an LOS. Link to post Share on other sites More sharing options...
RMweb Gold beast66606 Posted October 31, 2011 RMweb Gold Share Posted October 31, 2011 Phew and I thought it was a simple question Thanks for all the info For info - Widnes uses RailRoad & Co software to drive the signals and it simulates the SSI cycles, the feathers clear and a few seconds later the main aspect changes. Link to post Share on other sites More sharing options...
APOLLO Posted October 31, 2011 Share Posted October 31, 2011 Remember the old colour light signals at Kings Cross. The theatre indicators were back lit roller blinds, when the signal returned to on (red) it was interesting to watch the blind roll up / down through the indications to "blank". Would make an interesting model. Brit15 Link to post Share on other sites More sharing options...
Edwin_m Posted October 31, 2011 Share Posted October 31, 2011 On the SSI question (the 99.9% not interested please look away now - also any purists as this simplifies somewhat!) A SSI can be connected to up to 63 trackside functional modules (TFMs) which have up to eight inputs and outputs depending on type. Each TFM is polled in turn, when the SSI sends its output status and the module responds with the state of its inputs. The period to poll one TFM is known as a minor cycle, during which the SSI also processes one 63rd of its main data. The period to poll all TFMs is a major cycle, which cannot exceed one second or the SSI's timers will run slow. Also after a certain period of not hearing from the SSI, the TFMs will decide they have lost communication and shut down (locking points and turning signals to red). Assume the signal and the indicator are connected to the same TFM, which is the normal situation. When all the conditions are satisfied to clear the signal, including any approach control, then when the relevant TFM is next polled the route indicator is energised. However the route indicator proving circuit will not respond before that TFM replies back, so the message that it has proved will have to wait for the next time that TFM is polled nearly a second later. This will set the route indicator proving (rip) bit in the SSI memory that records the status of that signal. Sometime in the next major cycle the signal data is processed again and the appropriate aspect chosen, so that one cycle later the TFM is updated with the signal aspect. Thus two major cycles will elapse between the energising of the route indicator and the signal clearing. This period could be up to two seconds but will often be a bit less. It might be a bit longer if the indicator is connected to a lower-numbered module than the signal but I can think of no way of it being much more unless there is some fault in the route indicator proving circuit or possibly the trackside module or its communications bus. Certainly 30s is not credible for a simple interlocking-busy situation, as the TFMs would have shut down in the meantime. Link to post Share on other sites More sharing options...
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