Tablet Exchange

“He slowed to exchange Tablets, whistled a greeting, then gathered speed into the night.”

― Stepney's Special, Stepney the "Bluebell" Engine

In railway signalling, a tablet (or token, depending on the form of it employed on the railway) 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.

The tablet is often kept in a leather pouch with a hoop to be easily caught by the signalman or driver while the train is in motion, moving on to the next section. Sometimes they are exchanged by hand, while some railways have employed automatic catching apparatus.

In the Railway Series, in Stepney the "Bluebell" Engine, the tablet exchange system was seen in use on Thomas' Branch Line. Single line key-token instruments are also employed on the Bluebell Railway.

A token pouch was depicted in Thomas's Christmas Party.

In the television series electric key-token single line instruments can be seen in many signal boxes on the Island of Sodor.

In Thomas and the U.K. Trip, while visiting real railways, Gachapin and Mukku observe and explain how the tablet exchange principle works.

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.

Electric key-token single line instruments as well as token pouches were seen in Down at the Station segments.