Function: 1. Four-band 850/900/1800/1900MHz, can be used in global GSM network. 2. No call charges. The GSM relay receives a call from an authorized number, and then performs an on/off operation the first time it “rings”. 3. Security - Use the caller ID to identify and ignore unknown callers. 4. Add or remove users using the SMS text command. 5. There is no need to provide remote controls or buttons for different users. Specification: Characteristics: 1. Four-band 850/900/1800/1900MHz, can be used in global GSM network. 2. No call charges. The GSM relay receives a call from an authorized number, and then performs an on/off operation the first time it “rings”. 3. Security - Use the caller ID to identify and ignore unknown callers. 4. Add or remove users using the SMS text command. 5. There is no need to provide remote controls or buttons for different users. 6. Up to 200 authorized phone numbers can be configured at a specific time. 7. The relay will return an SMS message to the owner with a confirmation or authorized connection that the user can edit. 8. The time of closing or opening the relay is programmable. 9. With metal housing, IP30 rating. The metal housing and system are safely insulated, which is especially useful in industrial inspection applications. 10. Small size and support for wall mounting. 11. Many applications. Specification: Model: RTU5024 GSM Frequency: 850/900/1800 / 1900MHzNetwork Type: 2G Support: 2G, 3G, 4G Digital Output: NC/NO Currentless Contact, 3A/240VAC DC power supply: 9-15VDC/2A Power consumption: 12V, maximum input: 50mA / average 25mA SIM card: standard SIM card Antenna: SMA 50Ω antenna interface Temperature range: -20~ 60°C Humidity range: 90% relative humidity List of packages: 1 x GSM Mobile Phone Access Controller 1 antenna 2 terminals 1 x English Manual