1. Add or remove users via SMS text commands. Relay close or open time is programmable. 2. Can be operated anywhere, no distance restrictions. Quad-band, can be used in the global GSM network. 3. No need for remotes or buttons for different users. Safe - use caller ID for identification, unknown callers will be ignored. 4. 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. 5. 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 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". GSM frequency: Quad-band 850/900/1800/1900MHz Network: 2G 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: 50 ohm SMA antenna interface Temperature range: -20-60 Humidity range: 90% relative humidity Dimensions: 96.5 x 50 x 31.5mm/3.8 x 1.97 x 1.24inch color:Black Material:ABS Package Contents: 1 x GSM door opener Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.