A system of signalling, for Single lines, which is a system where the control of trains entering a section in advane is controlled by the accepting and carrying of the 'STAFF' or token, for the section. The object of the system is to prevent more than one train being in the section at one time, each signal box is equipped with a device for transmitting and receiving train working signals, as well as indicators to show direction of travel.
In use the following occurs, When a train is ready to be despatched into the section in advance, the signal man would hand the driver the 'STAFF' (obtained from the Electric Staff Machine after sending and receiving acknowledgement of the train described signal).
The train driver once in possession of the 'staff' now has the authority to proceed through the section, on arrival at the signal box in advance the 'staff is surrendered and placed in the staff machine, the driver is issued a staff for the next section in advance and so continues.
It will be noted that this system is an absolute system and only allows ONE train at one time to enter the section.
