Our GSM gate intercom incorporates a professional industrial grade GSM unit that receives calls at its SIM number as any ordinary GSM phone. When a visitor presses the call button on the unit it will call to one of three pre-set numbers. You can then speak to the visitor directly and open the gate from your phone. You can also trigger the gate to open from your phone by dialling the number of the units SIM card. The main advantages of this kind of system is that there is no need to leave your vehicle to trigger the gate and that you do not need a separate remote device. GSM frequencies: Quad band 850/900/1800/1900 MHz Power supply voltage: 9-24v AC 0r DC Current used in standby mode 70 milliamps Max current 2 amps Stainless steel vandal proof enclosure Backlit keypad (see picture) Standard 2g SIM card No landline required Dimensions L240 x W140 x H45 Operating temperatures -10 - +40c Signal strength function Stay active SIM card function 3 call points Digital key code access Phone list for direct access Hold gate open feature Pedestrian relay or door lock Easy programming using keypad Must be used with a minimum 3A power supply . We recommend the CP1250 power supply 12vdc/ 5 amp sold separately.