... sensor does – can accept? ------- It can accept unlimited wireless sensors including door,PIR sensor,vibration sensors,smoke sensor,gas ... yes,it can be compatible to three GSM frequence ,900/1800/1900 MHz,so it is available all over the world.4 ... Volume: 110dBStandard pack components1 main panel, 1 wireless infrared (motion) detector, 1 wireless door magnetic detector,1 siren, 2 remote controllers ...