Feature: Add or remove users via SMS text commands. Relay close or open time is programmable. Can be operated anywhere, no distance restrictions. Quad-band, can be used in the global GSM network. No need for remotes or buttons for different users. Safe - use caller ID for identification, unknown callers will be ignored. Up to 200 authorized phone numbers can be configured at a given time. One output with a relay rating of 3A/240VAC for connecting a door or machine switch. multiple applications. (doors, bollards, barriers, garage doors, shutters and access doors or machines). The relay action will return an SMS confirmation to the owner or authorized phone, this feature can be edited by the user. No call charges. The GSM GPRS trunk exchange rejects calls from authorized numbers and then performs an open/close operation on the first "ring". Specification: GSM frequency: Quad-band 850/900/1800/1900MHz Network: 2G Original output: NC/NO dry contact, 3A/250VAC DC power supply: 9-24VDC/2A Power consumption: 12V input maximum 50mA / average 25mA SIM card: Support 3V SIM card Antenna: 50SMA antenna interface Temperature range: -20-60 Humidity range: 90% relative humidity Material: Plastic Dimensions: 96.5x50x31.5mm/3.8x1.97x1.24in