Product Overview Great for entry detection for store front, safety sensor for garage doors, overhead doors security sensor, or other applications like offices, schools, warehouse, vehicle detection, etc. Retro-reflective design. Perfect for monitoring an entrance or use as an entrance indicator. Will make ding-dong sound or siren sound when the beam is interrupted. Speaker volume can be adjusted or turned off. When in siren mode, sounding time is adjustable from 3 to 30 seconds. 9VDC adapter included. All components plug into each other. No hard wiring required. Includes NIR retro-reflective sensor, reflector, speaker and 9VDC 200mA output adapter.