TD Berths

A train describer 'berth' usually, but not always, represents a signal. Train descriptions pass from berth to berth to show the movement of trains through a train describer area. Berths are referenced by four-character alphanumeric names:

Berth Name	Description
[0-9][0-9][0-9][0-9]	Numeric berths usually represent specific signals within a train describer area. Depending on the coverage of the TD area, these may also include signals from fringe boxes to show a queue of trains approaching an area. If a fringe signal shares a number with a signal within the TD area, it may be given a different first character (for example, if the fringe signal is 0453 and this is already allocated to a signal within the TD area, the berth may be named Q453)
[A-Z][A-Z][A-Z][A-Z]	Text berths represent sidings, fringe boxes or other special berths. These will be specific to the TD area, and are not found on signalling diagrams. They often represent trains waiting to enter a TD area, or trains sent to another area.
A***, B***, C***	A, B and C berths are often found on permissive platforms or bay platforms. They represent the first, second (and optionally, third) train descriptions waiting in the platform.
R***	R (Rear) berths usually represent a train arriving into a bay platform
LS** or **LS	LS berths (Last Sent) represent the last train descriptions sent to a fringe box or area. This is the most recent train to have been passed to that area's control.
STIN	Strike In: a train entering a train describer's area
COUT	Clear Out: a train leaving a train describer's area