This device allowed gangers to safely place a trolley, or carry out work, at remote locations on single line sections of railway without having to proceed to the signalbox to obtain the token.
The slides were interlocked with the token instrument, and released an "occupation key" as seen in the small device to the left.
The buttons on the main instrument would release keys at intermediate locations.
This instrument was to be found at Newtown, more information can be found in the Photo Gallery.