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A head marked at a single point on the rail.
Also known as: Counting head symbol, Wheel detector symbol
A signalling diagram symbol for a detector that counts axles past a point to determine whether a section is clear.
Marks a detector that counts axles past a point on a signalling diagram.
Contexts: Technical drawing
Is drawn at a point rather than over a length because it detects passage rather than presence, which is the whole difference between the two detection methods.
Contexts: Technical drawing
A small mark on one rail at a single point, unlike the track circuit which is drawn as a bounded length.