SECURITY:Use the caller ID to identify and ignore unknown callers. Add or users with the SMS Text command. There is no need to provide remote controls or buttons for different users. NO CALL CHARGES :No call charges, the GSM relay switch answers the call from the authorized number and then performs an on/off ope ion on the first "ringing". Just support standard 2G SIM card. APPLICABLE:Suitable for doors, elevators, garages, car parks, resorts, control rooms, warehouses, unsupervised machine rooms of the group type, such as telecom ope ors, on-site lighting subframes, base stations on site, traffic controllers and distribution of electrical system and field cabinet. HIGH QUALITY:The GSM gate opener with metal casing, IP30 protection level. The metal casing and system are safely isolated, especially suitable for in rial control applications. Small size and support for wall mounting. REMOTE CONTROL:This GSM door opener with a remote on/off switch for authorized calls for free calls, which can be ope ed from anywhere without distance restrictions. 850/900/1800/1900MHz quad band, can be used in the global GSM network.