GSM/2G Door Gate Opener Remote On/Off Switch Free Call

features remote on/off switch by authorized phone free calls, which can be operated from anywhere, no distance limit, very convenient.
Features:
*850/900/1800/1900MHz quad bands, can work in the worldwide GSM networks.
*No call charges. The GSM Relay Switch answers the call from authorized number then carries out the turn ON/OFF action on the first 'ring'.
*Secure - Using caller-ID for identification, unknown callers are ignored.
*Add or remove users by SMS Text command.
*No need to provide a remote control or keys for different users.
*Up to 200 authorized phone numbers can be configured at the specified time.
*The relay action will return a SMS confirmation to the owner or authorized call in number, this function is editable by user.
*The relay close or open time is programmable.
*Multiple applications. (Gates, bollards, barriers, garage doors, shutters and access doors or machines).