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Non-Described Special Description (NDSD)

Non-Described Special Description (NDSD)

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