Add or remove users by SMS mand. The relay or open time is programmable. Can be operated from anywhere, no distance limit. Quad-band, can work in the worldwide Networks. No need to a remote control or for different users. Secure - Using caller-ID for identification, unknown callers are ignored. Up to 200 authorized phone numbers can be configured at the specified time. One output with relay rating 3A/240VAC for connecting the switch of the door or machines. Multiple applications. (gates, bollards, barriers, garage doors, shutters and access doors or machines). The relay action will return a SMS confirmation to the owner or authorized call in number, this function is editable by user. No call charges. the GPRS Relay Switch rejects the call from authorized number then carries out the turn ON/OFF action on the first 'ring'. Frequency: Quad-Band 850/900/1800/1900MHz Gigital Output: NC/NO dry contact, 3A/240VAC DC Supply: 9-24VDC/2A Consumption: 12V Input Max.50mA/Average 25mA : Support 3V Antenna: 50 ohm Antenna Interface Material: ABS Color as shown Package Contents: 1 x Door Opener 1 x antenna Only the above package content, other products are not included. Note: Light reflection and different displays may the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.