The relay or open time is programmable. Can be operated from anywhere, with no distance limit. Works on global GSM networks. No need for a remote control or separate user devices. Uses caller-ID for identification; unknown callers are ignored. Up to 200 authorized phone numbers can be configured. One output with relay rating 3A/240VAC for connecting door or machine switches. Suitable for multiple applications such as gates, bollards, barriers, garage doors, shutters, access doors, and machines. Relay action sends an SMS confirmation to the authorized phone number; this function is editable. No call charges; the GSM GPRS Relay Switch rejects the call from an authorized number and performs the ON/OFF action on the first ring. GSM Frequency: 850 / 900 / 1800 / 1900 MHz Digital Output: NC/NO dry contact, 3A/240VAC DC Power Supply: 9-24VDC / 2A Power Consumption: 12V Input Max. 50mA, Average 25mA Supports 3V Antenna: 50 ohm SMA Antenna Interface Material: ABS Color as shown in image Package Contents: 1 x GSM Door Opener 1 x Antenna Note: Light reflection and different display settings may cause slight color differences between the image and the actual item. Measurement error allowed is +/- 1-3 cm.