STS No.12 Key Token Instrument

History

Token apparatus was pioneered from 1870 onwards by Tyer and Company Ltd., the early tokens taking the form of discs or tablets. Key token apparatus was first introduced in 1912 and with the greatly increased flexibility together with economy the system was widely adopted on single line railways all over the world.

Development of the instrument since the earliest days has been continuous and the latest instruments have many novel features and yet retain the component reliability which has been a feature of this design since its inception. Full use is made of die cast light alloys, thermo-plastic mouldings and rust-resisting alloy steels. Complete interchangeability of component parts is ensured by extensive tooling and quality control

Paints and plating finishes are of the highest quality with the object of ensuring long life with the minimum of maintenance in the severest of environments

General

The No.12 Key Token Instrument is a multi-purpose unit, the basic design being common to all applications. As the requirements for each application varies i.e. length and impedance of electrical line, type of operating function, accessories required etc., a separate design is produced to suit the individual application.

Application

It has long been accepted that the Key Token system provides the simplest and safest means of operating trains over a single line from one blockpost to another. The acceptance and retention of the token for that block section provides the driver with authority to occupy the line and only simple forms of signalling are necessary to ensure compliance with Operating Regulations. The token may also be used for such supplementary functions as the release of points for the occupation of an intermediate siding.

The first requirement of a token system is that extraction of a token from either end of a block section shall require the co-operation of both signalmen for that section and that it shall be impossible for a second token to be obtained (except where permissive working is in operation) until the token, already extracted, has been replaced in one or other of the section instruments.

Advantages

The instrument is extremely simple to operate, and easy to maintain. It is absolutely foolproof, and no tampering can take place.

The instrument is neat and compact. It has only one moving part, viz., an electrically controlled rotary commutator directly operated by the key tokens. A key token can be restored to the instrument from which it was withdrawn in the event of a train being cancelled, or after having been used for shunting purposes only a small amount of battery power is required. No permanent currents are necessary. A minimum of working parts and in consequence, a minimum amount of maintenance.

Optional Accessories

Further accessories which are available include:

a) The Key Token Balancer - a detachable unit which permits for the safe and efficient transfer of key tokens between instruments when out of balance working occurs. This situation occurs particularly when auxiliary instruments are employed.

b) The Key Token Stand - a ventilated metal cupboard onto which the instrument is placed which also provides space for the storage of the batteries which can be supplied as necessary.

c) Hand Generators

d) Telephones