a.two way communication b.use SIMCOM gsm module ... when alarm e.fine quality home gsm alarm systema.two way communicationb.use SIMCOM gsm modulec.with LED ... fine qualityModel:REH3201.Use SIM900B GSM module---industrial module .Two-way to communication,to talk with people who are ... PIR detector, a wireless door/window gap detectora siren, two remote controllers, a power supply, 1 manual product size: ...