If the Train Describer system detects an unidentified train stepping past a signal (and in certain other limited situations), it will automatically insert a non-described special description (NDSD) into the berth. Most manufacturers' systems will also generate a warning to the signaller in the form of an audible alert or visual message (or both). The NDSD will stay with the train like a normal description unless the signaller interposes the correct description over the NDSD.
The NDSD takes two forms. On the Southern region of the UK the format is:
* X * *
However, in the rest of the UK it is:
* * * *
NDSDs will never overwrite a real description. If a step occurs from a berth with an NDSD into a berth with a valid description, the NDSD is cleared out while the valid description remains. Note that older simulations may not incorporate this real-life feature.
Last edited by Steamer on 14/08/2020 at 16:08