Tablet Exchange

In railway signalling, a tablet is a physical object which an engine driver is required to have or see before entering onto a particular section of single track. The tablet is clearly endorsed with the names of the section it belongs to. A tablet system is used for single lines because of the greater risk of collision in the event of a mistake being made by a signalman or driver, than on double lines.

In the Railway Series, in Stepney the "Bluebell" Engine, the tablet exchange system was seen in use on Thomas' Branch Line.

In Hello Thomas and James, Thomas was waiting for another engine to pass and to allow the driver to deposit the token, in the form of a key, to the stationmaster.