ETT

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Electric Train Token (ETTElectric Train Token) is a system of controlling traffic over a single line.

Its most easily understood form is that where a token instrument is installed in the signal box at each end of the single line section thus forming an electrically connected pair. Each instrument has an electro-mechanical arrangement such that only one token can be removed from one of a pair of instruments with the cooperation of the signalman at the other end of the single line section. No other token can be removed until the originally removed token is replaced in one of the two instruments.

A token gives the driver of a train authority to occupy the single line section. Only in very exceptional circumstances may another train occupy or enter the section without being in possession of a token.

The SVRSevern Valley Railway uses Tyer's Key Token instruments. arleyekts.jpg

Much like a key for a mortice lock the end of the token that is placed into the instrument is made with four different "wards" to prevent a key being placed into the wrong instrument where multiple instruments are housed in one signal box. E.g Highley has an example of all four. Long sections to Bridgnorth and Bewdley North plus short sections to Hampton Loade and Arley.

Method of Operation