Timer-Photogate. U shaped with support rod. Use with the Multifunction Digital Timer SCE-199022, The IEC Photo Gate is a universal type device for detecting of the breaking of a beam of red LED light as objects move to pass through the beam. Very useful for many types of measurement and adaptors are available to permit the standard gates to 'click' to the edges of the IEC Air Track so that gliders can pass through. 12V,AC or DC is required to run the LED and any of IEC's many electronic timers will respond to the PhotoGate signal to do your bidding.