Add or remove users by SMS text command. The relay close or open time is programmable. Can be operated from anywhere, with no distance limit. Quad-band, compatible with GSM networks worldwide. No need to provide remote controls or keys for different users. Secure – 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 of 3A/240VAC for connecting to door or machine switches. Suitable for multiple applications including gates, bollards, barriers, garage doors, shutters, access doors, and machines. Relay action sends an SMS confirmation to the owner or authorized phone number; this function is user-editable. No call charges – The GSM GPRS relay switch rejects calls from authorized numbers and performs the ON/OFF action on the first ring. GSM Frequency: Quad-Band 850/900/1800/1900MHz Digital Output: NC/NO dry contact, 3A/240VAC DC Power Supply: 9-24VDC/2A Power Consumption: 12V Input, Max 50mA, Average 25mA SIM Card: Supports 3V SIM card Antenna: 50 ohm SMA antenna interface Material: ABS Color as shown Package Contents: 1 x GSM Door Opener 1 x Antenna Only the above package content; other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture to differ slightly from the actual product. Measurement error allowance is +/- 1-3cm.