How does this token system work? I really want to know how it works but know nothing on how signalling works in any shape or form, but I am really intrigued to know how this token signalling works. All I know is that the train stops at every signal to pick up a metal key but I don't know what they do with it or anything. Thanks
The purpose of the system is to ensure that only one train can be in the single line section at any one time.
At its most simple, this is achieved by the use of a single staff (often no more than an appropriately marked block of wood!) which must be carried by every* train entering the single line section. The obvious problem with this system is that, once a train has passed through the single line in one direction, it's then not possible for another to follow until the staff has been returned to the start of the section, so its use is restricted to dead-end branch lines with no facility to shut inside at the terminus (like Rufford - Ormskirk, mentioned above). The One Train Working regulations apply in these cases nowadays.
Staff and ticket working, where the Driver of each train was shown the staff before entering the section (thus proving that nothing was coming from the other end) but not necessarily carrying it with him (being given a ticket if not), was an improvement, as it meant that more than one train could pass through the section in one direction without the need to transfer the staff back after each. It wasn't the most flexible though - if the staff somehow ended up at the wrong end of the section (perhaps because the train which was to carry it through was cancelled), you were stuck! I don't know if this is still in use anywhere on Network Rail (I have a feeling it was used somewhere on the Blyth & Tyne until recently?), but the NYMR uses it (or did, at least) south of Goathland.
Electric token block, where a number of tokens were available for each section, shared between (and electrically locked inside) the token instruments in the signal boxes at either end of the section, provided the flexibility that was lacking under staff and ticket. The very clever (and quite simple, at least according to the S&T) interlinking between the two instruments ensured that only one token could ever be removed at any one time, requiring the co-operation of both Signalmen - until that token is restored (at either end of the section), it's impossible to withdraw a second token. The Electric Token Block regulations apply here (worth a read), but the system has been developed further in some places to allow token instruments to be operated by Drivers under the supervision of a single Signalman (e.g. Nunthorpe - Whitby).
* - with a few exceptions, like going into an occupied section to assist a failure etc., or when Working by Pilotman is in operation.
