1、It can be operated from anywhere without distance restrictions. 2、GSM temperature monitoring alarm can reject calls from authorized numbers without making a call. 3、Users can dial the device number by authorization number. The device will automatically refuse to receive and immediately send short messages of the current status (temperature and voltage) to the caller. 4、Multiple applications (temperature, power state, solar panel, DC voltage). 5、Up to 10 authorized phone numbers, 5 can be used to answer calls or text messages, and 5 can be used for calls and text messages to generate alarms. Features: It can be operated from anywhere without distance restrictions. GSM temperature monitoring alarm can reject calls from authorized numbers without making a call. Up to 10 authorized phone numbers, 5 can be used to answer calls or text messages, and 5 can be used for calls and text messages to generate alarms. Monitor external AC power status, AC on/off will send SMS to authorized phone number. The built-in MCU has a measurement range of 0-36 VDC, eliminating the need for additional sensors and saving costs. Set it once every once in a while (the user can set the time by himself) and automatically send its status to the authorized number. Support remote reading of historical data via SMS. Supports TCP and  RTU over TCP protocol for cloud monitoring. Rechargeable backup battery lasts for 8 hours. Use caller ID and password to identify and ignore unknown calls. Can be programmed via SMS protected SMS command or APP. Based on GSM network, it is suitable for many applications. Automatically restart the cycle by remote reset and restart via SMS. Specifications: Condition: Brand New Color: Shown as Picture Material:  ABS Plastic Power Consumption: Standby: 12V/20mA; Maximum Power Consumption: 12V/150mA GSM Frequency: 850/900/1800/1900MHz SIM Card Interface: support 3V SIM Card External Antenna: SMA Antenna Interface, 50 ohms Support Protocol: RTU Over TCP protocol, TCP protocol AIN Range: 4-20 mA Built-in Battery: 3.7 V/900mAh(Included) Working Temperature: -10 ° C ~ 60 ° C Operating Humidity: Relative Humidity 95% (no condensation) Size: Approx. 70mm * 88mm * 30mm/2.8 * 3.5 * 1.2 in Package List: 1 * GSM Monitoring Alert 1 * Antenna 1 * Power Adapter 1 * Instruction Manual