|Talyllyn: The World's First Preserved Railway|
|1. A Gray Day at Tywyn||5. Changing Ends|
|2. The Honorable Rituals||6. Conversation at Abergynolwyn|
|3. An Iron Horse Indeed||7. Down Train|
|4. Ascent to Nant Gwernol|
|Talyllyn Railway: Train Control|
Abbott explained it, the train staff or
token system relies on the division of the Talyllyn's main line into defined blocks, or
sections. These sections are clearly defined in the employee timetable. To
move into and occupy a section, a train's driver must receive the "token" or
"train staff" for that section and direction of running. Only one token
can be issued for any given section of line at a time: thus, the driver holding a token
can assume that he or she is in sole possession of that section of line, and will
encounter no other trains, either leading or opposing, along the route.
At the end of a section the train stops, and the driver returns the token for the section he is vacating. One of three things then happens: the driver receives the token for the next section, and the train proceeds; or, the driver is instructed to wait until a preceding train clears the block ahead and surrenders the token at the far end, upon which time he can be issued the token and permission to proceed; or, the driver is instructed to take siding, clear the line for an opposing train, and wait for that train to arrive, after which he can receive its token and proceed.
Schematically, then, the token system is very similar to the track warrant system now very common among mainline American railways. However, the magic of the system is its physical equipment. First, there is the novelty of having the "track warrant" embodied in a physical symbol: a metal disk or key one can touch and hold. And then there are the ingenious token machines.
In its early days, the train staff or token system relied on human operators. A man would be posted in a cabin at each section point, with the section points connected with one another by telegraphs. When a train entered a section, the operator would issue the appropriate train staff to the driver. He would also immediately telegraph ahead to inform his counterpart at the other end of the section that the staff was out, and no opposing train should be admitted to the section. One the train had handed in its train staff at the far end, that operator would notify his colleague back at the beginning that the train staff was in, and a new staff could be issued. This required extensive manpower, and scrupulous recordkeeping on the part of the operators.
or EKT machine at
of the Talyllyn
train staff system only reached its highest
form when the staff was combined with the concept of interlocking electromechanical
machinery-- the system preserved and used today on the Talyllyn under the loving care of
signaling engineers Ian Dods and Richard Huss. In this refinement, the human cabin
operators are replaced by pairs of token machines. At the beginning of each section,
a train stops, and the driver dismounts and approaches the token machine to request a
token for the line ahead. Before releasing the token, the machine checks an
electrical circuit running to its opposite number at the other end of the section.
Only if that machine has not issued a token for the section does the machine at our end
unlock, and allow the driver to withdraw his token. The train holding the token is
thus protected from either end, and guaranteed exclusive occupancy of the section.
Only once the token has been returned to the machine at the far end does either machine
permit another token to be issued.
Simple, foolproof, and eminently safe, the electric token system provided an efficient means of traffic control for secondary and branch lines throughout the British Empire. By maintaining such a system in daily operation, the Talyllyn furthers its mission to preserve not simply the engines and cars, but the entire technological fabric of British steam railroading in its glory years.