Simply; This is the best non-Thatcham approved system you can get. Based upon our CAT1 Thatcham system, we have basically 'copied and pasted' some items from the CAT1 and made it into the CAT3.1. The CAT3.1 supercedes the CAT3 by the addition of several useful features, and now includes; •Remote controlled unit •Fully encapsulated electronics for 100% waterproof construction •Surface mount technology for reliability •Waterproof Remote Transmitter with multi-coloured LED display •User definable Nudge Sensor •A 'Proper' movement sensor - unusual in the budget end of alarms •Hot wire / forced ignition sensing •Class-leading low Current draw - less than 5mA •Audible confirmation of arming/dis-arming •Cool BLUE LED status indicator •Hazard light flash on arming and dis-arming •Automatic Arming option - 55 seconds after ignition is switched off •Movement sensor adjustability from the key fob •'Ferry' mode •External, louder siren upgrade available. See related products Don't Forget! The Acumen CAT3 and CAT3.1 can be upgraded to the CAT1 Flip-Fob, and can also be connected to the external Extra-loud Siren and the optional Starter Immobiliser.