HTQ1021: Features: -Panel-Operates for months on a single lithium battery-Ultrasonic operation will not interfere with or be affected by other electronic devices-Just wandering by or sleeping next to the door-Dual range controls let you set independent inside and outside activation distances-4-Way access control lets you select from in only, out only, full access or closed and locked-Optional, auto-recharging battery back-up protects against power outages-Requires optional battery-Battery only (Requires optional charger kit)-Automatic deadbolt lock, safety retract system. Includes: -Standard AC wall adapter (included). Options: -Available in Medium and Large sizes. Specifications: -3 Power modes. Dimensions: -Medium dimensions: 85" H x 4.5" W x 17.5" D-Large dimensions: 85" H x 5" W x 22" D.