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 additional hardware for different users. Uses caller-ID for identification; unknown callers are ignored. Up to 200 authorized phone numbers can be configured at specified times. One output with relay rating 3A/240VAC for connecting to door switches or machines. Suitable for multiple applications such as gates, bollards, barriers, garage doors, shutters, access doors, or 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 Only the above items are included; other products are not included. Note: Light reflection and differences in display screens may cause slight variations in color between the image and the actual item. Measurement error allowed is +/- 1-3 cm.