1. Input voltage range: 5V-18V DC. 2. Self-ejecting SIM card slot design accepts 2G/3G/4G SIM cards or mini SIM cards from China Mobile or China Unicom. The module automatically powers on and connects to the network when powered on, eliminating the need for button activation. 3. User-controlled power on and off. Direct startup upon power-up eliminates the tedious startup process, with a reserved power-on pin. 4. The module features TTL level conversion circuitry, making it compatible with various microcontroller serial ports. Direct connection without conversion required. 5. Audio interface pinout for easy testing, with reserved headphone and microphone connectors. Supports TTS/DTMF functions, enabling direct text playback and keystroke recognition during calls, enabling integration with the 10086 voice control system. Bluetooth 3.0 protocol, enhanced Bluetooth antenna for exceptional signal strength, supporting OSPP and audio services. Reserved BAT port for lithium battery power, allowing for project development with either a 3.7V lithium battery or an 18650 lithium battery (not included). Reserved IPEX D-type connector, SMA connector, and spring antenna connector for adapting to different antenna needs. Features an operating indicator: The LED flashes every 1 second when there's no network, no SIM card, or the SIM card is inserted incorrectly, and flashes every 3 seconds when connected to the network. Color: As Shown Material: Plastic+Metal Package Contents: 1 * Development Board 2 * Pin Roll 1 * Antenna