Deleted
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Post by Deleted on Jul 30, 2005 21:48:29 GMT
What performs the modern equivalent of "block bells" in LU signal boxes today, i.e. presentation/acceptance of trains between areas of control...
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Tom
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Signalfel?
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Post by Tom on Jul 30, 2005 22:29:31 GMT
The equivalent I would guess is the Train Describer, though unlike BR practice where the signalman has to accept the train, the TD system on the underground merely advises where it is going and the signal operator doesn't accept or decline the train offered to him/her.
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Post by Deleted on Jul 30, 2005 22:31:17 GMT
Interesting. What sort of system is used between someplace like Baker Street and someplace like Neasden?
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Tom
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Post by Tom on Jul 30, 2005 22:37:31 GMT
Each train has a Train ID (TNID) which corresponds to it's number and trip. The centre computer at Baker St corresponds track occupancy with the TNID and when the train gets to Green Park, as the train drops a track circuit at the boundary the TNID is passed from Baker St to the Centre Computers at Neasden.
As it's a case of computers talking to computers it's fairly simple. When computers have to talk to TD things get more complicated, and I'll go into that if you want when I'm more awake...
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Post by q8 on Jul 31, 2005 10:32:18 GMT
I'll add a bit Tom if I may
From a passengers point of view certain track circuits are "transmitting" circuits for want of a better word. These circuits while still part of the normal signalling system do two things when dropped. They return/maintain the associated signals to/at danger and also send the description from a previous section forward as well. A Description section is much longer that a normal signalling section however.
As an example let us assume you are standing on the eastbound platform at Victoria and the train indicator is blank. When an easbound train leaves South Ken and gets halfway to Sloane Square he will drop a ceratin circuit that sends the description forward from South Ken to Embankment (the next controlled area) As he drops that track the train indicators on the platforms will illuminate to say he is coming and how long. The indicators will only light up as far as Embankement when the process is repeated for transmission forward. The sending forward of descriptions also shows up on the various desks in the control room.
As the train moves forward along the line so does it's description. I 'll give you a further example. As you know Bromley-by-Bow to Dagenham East comes under the control of Barking signalbox. Now he gets a train come up Bow Bank and drop on his diagram as it does so. It brings with it it's description (Upminster). The description will only show up on the indicator at Bromley and no further and also on the describer in the cabin for Bromley.
As the train leave Bromley and puts the starting signal to danger the action of doing that will send the description forwards to the indicators at West Ham and Plaistow and the describer in the cabin for Plaistow. As he leaves Plaistow the whole cycle is repeated and the description is forwarded to East ham and so on throughout the whole portion of the line under the control of Barking Cabin
So you see while signalling sections are relatively short, description sections are from controlled to controlled area. That's the general way of it as I recall.
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Post by banana on Jul 31, 2005 11:08:49 GMT
How come at Putney Bridge (Eastbound) the train description is incorrect a lot of times?
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Tom
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Post by Tom on Jul 31, 2005 15:03:43 GMT
Probably dodgy info coming over from Wimbledon, unless the old WARS computer has been updated in the last five years.
(WARS = Waterloo Area Resignalling Scheme)
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Deleted
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Post by Deleted on Jul 31, 2005 19:32:45 GMT
its because of the interface between the WARS system and the LUL t/d system the t/d's are actually put up at putney bridge not at wimbledon usually the descriptions go right as the train enters the platform but on the w/b the descriptions on the dot matrix screw up because of a faulty cable between fulham broadway - parson's green
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Post by banana on Jul 31, 2005 22:12:18 GMT
iusually the descriptions go right as the train enters the platform You could be right there, but by then I'm at the north end of the platform and the t/d only shows south  |
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