About the TD feed and S-class messages - documentation and completeness of coverage
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Aleksa Jakovljevic
Sep 19, 2025, 7:44:54 PM (2 days ago) Sep 19
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Hi all,
I've been having a hand at trying to process the TD feed and decided to try to include all the data from both the C-class (TD berths) and S-class (signals, track section occupation, point position, &c) messages in a nicely formatted page (i.e. explained simply, I'm using PHP to dynamically update CSS formatting on a custom font to show TD berths, track occupancy, &c).
As a learning experience I focused on a small area where I had good documentation (signalling diagrams and/or panel pictures, among others) and settled on the Wilton Jn. area just west of Salisbury station. I've attached a couple of screenshots from my implementation: sections for which I am pretty confident in the accuracy of the on-wiki mappings are in yellow, there's one section in green whose occupancy can be mostly deduced from the presence of a describer in the berth and the occupancy of adjacent sections, everything for which I have no data is in grey - in addition there are a few test bits at the bottom.
The TD berths all step-up as expected. However, I've tried following the decoding scheme from the wiki for the S-class messages but realise that this data - beyond some TCs on the panel which appear to have been combined into a single data bit - appears to be incomplete. I don't know if this is related to the fact that there are several bits which never seem to be updated either. I figure this probably isn't a priority use case of this data, but while I'm at it, has anyone encountered this issue previously? Does anyone know if there's more complete documentation available somewhere else?
Cheers and thanks for any answers which help clarify this,
AJ
I've been having a hand at trying to process the TD feed and decided to try to include all the data from both the C-class (TD berths) and S-class (signals, track section occupation, point position, &c) messages in a nicely formatted page (i.e. explained simply, I'm using PHP to dynamically update CSS formatting on a custom font to show TD berths, track occupancy, &c).
As a learning experience I focused on a small area where I had good documentation (signalling diagrams and/or panel pictures, among others) and settled on the Wilton Jn. area just west of Salisbury station. I've attached a couple of screenshots from my implementation: sections for which I am pretty confident in the accuracy of the on-wiki mappings are in yellow, there's one section in green whose occupancy can be mostly deduced from the presence of a describer in the berth and the occupancy of adjacent sections, everything for which I have no data is in grey - in addition there are a few test bits at the bottom.
The TD berths all step-up as expected. However, I've tried following the decoding scheme from the wiki for the S-class messages but realise that this data - beyond some TCs on the panel which appear to have been combined into a single data bit - appears to be incomplete. I don't know if this is related to the fact that there are several bits which never seem to be updated either. I figure this probably isn't a priority use case of this data, but while I'm at it, has anyone encountered this issue previously? Does anyone know if there's more complete documentation available somewhere else?
Cheers and thanks for any answers which help clarify this,
AJ
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