14-04-2010, 11:01 PM
(14-04-2010, 02:20 PM)sugavanam nagarajan Wrote: Dear Sir,
1.Please explain the working principle of train describer:
How unique train number is identified by TD?
2.Is it SSI only having SPAD Alarm or RRI also?
Explain how SPAD Alarm system is working?
-Sugavanam
The TD does not identify anything unique about the train number. It is merely a series of "addresses" in a memory into which train numbers, or "descriptions" can be entered. There is no sense checking of the data. You could have the same train description in every berth of a train describers memory and it would not bat an eyelid at you. In fact, during engineer's possessions, I have seen areas of the signaller's control panel where they have entered *T3* into every signal berth to remind them of the extent of the possession (T3 is the module of the UK rule book which covers engineers' possessions). What is "clever" about a TD is the fact that it will step the a given description from a specific berth into another one depending on the rules programmed into it and the routes that have been set so that a train description (whether entered correctly or not) will follow that train where ever it legitimately goes.
Both SSI and RRI can have SPAD alarms since SPAD alarms are a function of the display system and not the interlocking. I am not an expert, but they are effectively an extension of the fact that in the past, a TD would have given an alarm if a "step" occurred (ie a track became occupied) when no correct route had been set. Effectively it was saying "something should be in this berth but I don't know what because there was no route set for me to know where the train has come from". If you extend this functionality to highlight to the signaller which signal has the occupied berth, rather than just give an audible alarm to say this has happened somewhere on the panel, you have the basics of a SPAD alarm.