Feature: Add or remove users via SMS text commands. Relay close or open time is programmable. Can be operated anywhere, no distance restrictions. Quad-band, can be used in the global GSM network. No need for remotes or buttons for different users. Safe - use caller ID for identification, unknown callers be ignored. Up to 200 authorized phone numbers can be configured at a given time. One output with a relay rating of 3A/240VAC for connecting a door or machine switch. Multiple applications. (doors, bollards, barriers, garage doors, shutters and access doors or machines). The relay action return an SMS confirmation to the owner or authorized phone, this feature can be by the user. No call charges. The GSM GPRS trunk exchange rejects calls from authorized numbers and then performs an open/close operation on the first "ring". GSM frequency: Quad-band 850/900/1800/1900MHz Network: 4G Output: NC/NO dry contact, 3A/250VAC DC power supply: 9-24VDC/2A Power consumption: 12V input maximum 50mA