This Photogate is a self contained light source and photo detector mounted and aligned in a plastic ‘U’ frame. It is complete with an 8mm diameter x 200mm long mounting rod which can be clamped in a bosshead to allow the Gate to be adjusted to any angle in any direction. One side of the gate contains the solid state LED visible light source which operates from an 8-12V.AC or DC power source. The power to run the light source is via 4mm banana sockets. The opposite side of the housing is the photo detector which behaves as an electronic switch that closes when light beam is broken. A monitor LED on the side of the housing lights indicates that the gate has switched and this monitor feature is very useful when setting up for an experiment. The 4mm connection sockets are polarised positive and negative. A digital Timer is connected to these sockets. If connections are backwards, the Gate will appear to be permanently switched on.