hi,just fitted one this week and its great,best ever.we have the 500/5 bailey 2003.i wanted an alarm for some time and was lucky to find one from a new caravan when he changed the system,updated to a remote one.one of the hardest things i found (auto electrician) was routing the PIR wire this is a very long cable and must not be wound in a coil.drilling holes in my pride and joy hurts.with the PIR if you have the large skylight on the roof it needs not to see this because of sun light,locating under a shelf solved this.did not use the tow sensor,green wire.yes thats another thing only three wires to connect,makes it easy for DIY.any more information required please ask.you need also to drill a 50MM hole in the floor under the siren and tilt sensor,this must be sealed (silicone) on the inside edges.hope this helps i wish i had done it sooner.disconnect battery before doing any connections.ONLY CONNECT THE PIR + NUMBER PANEL AFTER CONNECTING TO THE BATTERY