A standard B.R. 3 position block repeater instrument.With the demise of so many manual signal boxes and crossing gates these are now getting fairly rare in this area. This example was recorded at Milton crossing in the section between Chesterton Junction and Waterbeach boxes on 5th June 1978. In this scenario a train is between Coldham Lane signal box, Cambridge and Chesterton Junction. Probably just enough time for the crossing keeper to quickly let a vehicle over the crossing.