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| Interposing TDs on PSBs 03/05/2014 at 11:23 #59972 | |
belly buster
368 posts |
Having 0.0 knowledge of PSBs I was looking at the photo currrently on the SimSig homepage and was curious as to how the TDs get interposed on the layout.
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| Interposing TDs on PSBs 03/05/2014 at 11:32 #59975 | |
GW43125
495 posts |
I believe there is a separate TD describer computer to do this. Feel free to correct if wrong, Hope this helps, DSW Log in to reply The following user said thank you: belly buster |
| Interposing TDs on PSBs 03/05/2014 at 11:47 #59978 | |
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belly buster
368 posts |
" said:I believe there is a separate TD describer computer to do this.That makes sense. But what did they do in the 1960s when these PSB first opened? Log in to reply |
| Interposing TDs on PSBs 03/05/2014 at 11:54 #59980 | |
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Danny252
1461 posts |
The way it works now at Swindon is you simply input a TD ID, followed by the description you want. I would imagine there was a similar method back in the day when it was all runs off relays - just a lot more clicking and clunking going on!
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| Interposing TDs on PSBs 03/05/2014 at 13:08 #59983 | |
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Jan
892 posts |
An example can be seen in the documentary about the opening of Dartford PSB (First Of The Thirteen). This is the relevant bit: [video width=425 height=344 type=youtube]Blmg4dUONXU?rel=0&start=431&stop=477[/video] Two million people attempt to use Birmingham's magnificent rail network every year, with just over a million of them managing to get further than Smethwick. Last edited: 03/05/2014 at 13:10 by Jan Log in to reply The following user said thank you: belly buster |
| Interposing TDs on PSBs 03/05/2014 at 13:44 #59984 | |
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Danny252
1461 posts |
Looking at the number of buttons and which one he presses for "U", am I right to think that two letters are/were unavailable? If the whole alphabet wrapped around over the buttons, I'd expect U to be two buttons to the right, and there would be two too many letters to fit into the two "shift" buttons. Or were two letters placed at the end during "numerical" mode, for which there are two too many buttons? Last edited: 03/05/2014 at 13:45 by Danny252 Log in to reply |
| Interposing TDs on PSBs 03/05/2014 at 14:11 #59985 | |
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Late Turn
696 posts |
I seem to remember that there were indeed two letters missing from early TDs - possibly U and W, which is the most likely explanation that I've heard for interregional trains to the Western running as xVxx!
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| Interposing TDs on PSBs 03/05/2014 at 17:18 #59994 | |
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Danny252
1461 posts |
Well "U" can't be missing, as the video shows the signalman inputting a 5Uxx headcode! "C" is in the position I'd expect it, but "U" is two over to the left, which would suggest that two letters between C and U have been removed/placed elsewhere. "I" seems a likely candidate for non-inclusion.
Last edited: 03/05/2014 at 17:20 by Danny252 Log in to reply |
| Interposing TDs on PSBs 03/05/2014 at 17:35 #59995 | |
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Late Turn
696 posts |
D'oh, of course!! Must be the warm weather getting to me...
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| Interposing TDs on PSBs 03/05/2014 at 18:27 #59999 | |
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JamesN
1580 posts 
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I and Q stand out as the most logical candidates to me
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| Interposing TDs on PSBs 03/05/2014 at 22:13 #60012 | |
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Cedric
42 posts |
Train describers in 1960's style PSBs used cathode-ray tubes (CRTs) except on the Western where the describers were electro-mechanical. CRTs produced slightly fuzzy images. "W" was not used due to the amount of space used up (hence inter-regionals being given a "V" headcode for the Western) and neither was "I" because it is easily confused with "1". Cedric Log in to reply |
| Interposing TDs on PSBs 04/05/2014 at 00:05 #60014 | |
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Muzer
718 posts |
Electromechanical? Cool, as in the old mechanical dot-matrix displays, or something else?
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| Interposing TDs on PSBs 04/05/2014 at 00:55 #60015 | |
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belly buster
368 posts |
" said:Train describers in 1960's style PSBs used cathode-ray tubes (CRTs) except on the Western where the describers were electro-mechanical. CRTs produced slightly fuzzy images. "W" was not used due to the amount of space used up (hence inter-regionals being given a "V" headcode for the Western) and neither was "I" because it is easily confused with "1".Interesting. I did a bit of googling and found some more info here http://forum.signalbox.org/viewtopic.php?f=6&t=3816 Log in to reply |
| Interposing TDs on PSBs 04/05/2014 at 07:43 #60017 | |
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Cedric
42 posts |
The WR displays had the digits and letters on rotating drums on a separate diagram mounted vertically behind the main panel. You set it up using a telephone-style dialer, and yes it was all driven by relays and things. The description would step forward in parallel with the tract circuits on the diagram below. Sadly I never saw one in action - I was a "Southern" man mainly and although I worked on the WR in the late 1980s by then they had all been removed as they were pretty high maintenance. There may be others on the forum who can tell you more. The CRTs were also replaced as soon as there was better technology. A CRT unit is relatively expensive, needs high voltage and when the same images are repeatedly shown the screen starts to "burn", destroying the image quality. As well as CRTs there were also "edge-lit perspex" screens. There was still one in the describer at Willesden HL Sisings (also known as Willesden No 8 box) - a fringe to Willesden PSB - which I was passed out for and operated occasionally in the mid-70s. Each of the four train characters had its own perspex unit with a series of bulbs and filters. Depending which bulb was lit up you would get different characters displayed on the screen (I think that was how it worked!) The displays were clearer than CRTs but the one in No 8 box was not terribly reliable - the bulbs kept blowing and the S&T did not see us as high priority! Log in to reply |
| Interposing TDs on PSBs 04/05/2014 at 13:16 #60030 | |
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Haraubrad
103 posts |
I can remember working to Oxford panel with the describer on drums. it was towards the end of the describers life and when a train entered it could have an entirely different description when it reached Oxford Station. One day a freight Liner was routed into the up bay as it's description had altered. Unfortunately the Driver took the route. It was quite a performance setting him back out
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