1. DC6-24v wide voltage power supply, can be used with your system power supply. High-performance DC-DC power supply circuit with protection, greatly improving system stability 2. Support 3.3V/5V TTL level control, convenient communication with common microcontrollers, such as Ard/51/STM32.The module lists TX/RX/GND separately, which is convenient to use. 3. With standard serial port interface, it can be easily controlled or debugged by PC 4. With headphones and mic interface, it is convenient to test GSM voice call function 5. With SIM card electrostatic protection chip, protect against static electricity generated when plugging in SIM card 6. All available SIM800c pins are out, allowing you to develop SIM800 applications. 7. With backup battery 8. With NET_STA indicator, it is convenient to watch current SIM800c status. Colour:Black Material:ABS Size:10x6x3cm Package Contents: 1 * Module Only above package content, other products are not included. Note: Light and different displays may cause color of item in picture a little different from real thing. The measurement allowed error is +/- 1-3cm.