The Seco-Larm Door Entry Chime is perfect for garage doors, overhead doors, or entry detection for store fronts. When the beam is broken by a visitor, the chime alerts you. Other applications: offices, schools, warehouse, vehicle detection (driveway alert), etc. FEATURES: Retro-reflective photoelectric sensor. Range: Up to 22 feet (7m). Perfect for monitoring an entrance, or for counting foot traffic with optional counter. 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. All components plug into each other. No hard wiring required.