Trains running on single lines have invariably carried a token of sorts, the possession of which was authority to be on the line. We take a brief look at the various systems that were in use, from the simple One Engine in Steam staffs to the electric token systems that had many tokens, but electrically interlocked so that only one token could be issued at a time.
For a far more detailed description of electric token systems, refer to David Stirlings excellent paper on the subject, published by the Signalling Record Society.
One Engine in Steam
This is the simplest of the systems for controlling movements over a single line. There is only one staff, which has has to be in the possession of the driver. As there is only one staff it follows that trains have to alternate up and down the line. Although a simple system it does have its drawbacks, on a through line, if trains do not follow the time table for whatever reason, you could end up with the staff at the wrong end of the section. The system suits dead end branches with light traffic.
Kings Lynn - Middleton Towers staff, for the freight only branch, still in use (2005)
Train Staff & Ticket
A development off the One Engine in Steam system, again with only one token in the form of a staff. Increased operational flexibility is achieved by the virtue of being able to issue tickets to enable more than one train to proceed in the same direction.
The tickets were stored in a ticket box, the box could only be opened by the staff for the section. The staff could only be withdrawn from the ticket box if the lid was closed.
If more than one train was to proceed in the same direction the box was opened, a ticket withdrawn and filled in. The driver was shown the staff, but given the ticket, which combined with seeing the staff was his authority to enter the single line (subject to obeying signals of course). Any number of trains could be dispatched in the same direction, the last train would be given the staff. Once the staff was at the other end of the section, trains could now proceed in the other direction.
The system was not foolproof as there was nothing stopping more than one ticket being withdrawn from the box at a time, it relied on the driver being shown the staff to prove the tickets validity.
Note: In some situations the tickets were made of metal and reusable. Also paper tickets could be of different shapes as well as colour.
Staff and ticket box for Watton - Roudham Junction, along with completed ticket.
|TYER No 1 tablet Instrument
The first electric token instrument to be produced was by Edward Tyer, patented in 1878 and introduced in 1880 on the Calander and Oban Railway. The tokens were in the form of iron discs (tablets) xx" in diameter usually with a brass face with the section engraved upon. Tablets were withdrawn from the slide at the bottom and returned via the hinged lid on top of the main body. The main disadvantage with this instrument was that once a tablet had been withdrawn it had to pass through the section to the other end, it could not be restored to the instrument that issued it. This could cause major delays if a train failed or was delayed for what ever reason.
To get over this obvious disadvantage most instruments were modified around the turn of the century to bring them up to modern standards, this involved incorporating the top and internals from the then current No 6 instrument.
Last in use in Scotland, until 1979.
The photo depicts a modified instrument at Weybourn on the preserved North Norfolk Railway.
|TYER No 6 Instrument
A development of the No 1,2,3 & 4 instruments, the No 6 was introduced in 1892, and was destined to became the most popular of the tablet instruments. Virtually all railway companies used this instrument at some time.
The tablets were withdrawn and replaced from the instrument via the slide at the bottom, combined with manipulation of the handle on the side.
The tablets were in the form of round discs xx" in diameter, and were made variously out of iron (with a brass face), aluminum or fibre. When the lighter materials were used it was not uncommon for a weighting tablet, made out of iron, to be placed on the top of the column of tablets, to stop the tablets from cocking and thus jamming the instrument up.
These instruments are still in use on BR (2005), confined to the Stranraer route in Scotland.
No 6 instrument at Weybourn for the section to Sherringham
RSCo Large Staff Instrument
Tyers monopoly of the electric token market was broken in 1890 with the introduction of the large staff instrument. The design was first patented by Webb and Thompson of the London and North Western Railway in 1988 and the license for production was given to the Railway Signal Company who marketed the instruments.
The tokens were in the form of steel tubes about 24" long, reminiscent of the old staffs. There were five brass rings on the staff, four of which engaged with the mechanism in the head of the instrument and a fifth ring, placed in one of four positions to prevent staffs of adjacent sections being placed in the wrong instrument.
Last in use on BR in 1981
RSCo Miniature Train Staff Instrument (M Type)
Introduced in 1906, the 'M' type was electrically identical to the Large Staff instrument but everything was reduced in size, the staffs being only 10 3/4" long.
No longer in use on BR, but still to be found in use on the Festiniog Railway in Wales.
RSCo Miniature Train Staff Instrument (S Type)
Introduced shortly after the 'M' type, the 'S' was slightly smaller again, the staffs being typically 9" long. Although of broadly the same appearance, the instruments were quite different electrically.
No longer in use on BR
Clonmel (Ireland), instrument for the Clonmel to Tiperary section, still in use (2005)
TYER Key Token Instrument
North Walsham, instrument for the North Walsham to Wroxham section.
RSCo Key Token Instrument