The Window was dispensed using the Window Launching Machine Mk.1a (RELAWM35359.001). The machine consisted of an aluminium alloy box, containing three levels of trays for packets of Window. The trays were actuated by a system of chain drives and belts, which fed the individual packets to a chute at the rear of the machine. The chute then dispensed the packets through a hole especially cut in the bomb bay doors of a bomber aircraft. The machine was controlled by the navigator, using a Switch Box fitted with a control switch and indicator light that illuminated as each bundle of Window was released. A formation of aircraft fitted with the machine could release a carefully controlled pattern of Window, efficiently jamming the German radar.