Never turn on or off your radio(s) again! The APS-12 is basically a voltage controlled switch. When the vehicles engine shuts off, the unit senses the drop in voltage and starts the APS-12 timer to automatically shut off after 2 min. to 12 hrs. •User adjustable shut down delay: 2, 15 or 30 minutes and 1, 2, 3, 4, 5, 8 12 hours. •Rugged, water proof construction. Easily installed in engine compartments or high vibration environments. •Super low standby current draw of 4 mAh will not drain your battery. •Smart! No ignition wire is required. •Overvoltage protection: Automatically shuts off at 16V with Auto reset •Amperage Rating: 25 Amps max @ 12V continuous duty •Compact Size: 3½"L x 2"W x 1½"H •Weight: 0.5 lbs. (229 grams)