1. On-board mature and stable ESP-12F Wi-Fi module with 4MB flash memory; 2. I/O port and UART download port are fully accessible for easy secondary development; 3. Power supply supports AC 90-250V, DC 7-30V, and 5V; 4. Built-in reset button for the Wi-Fi module; 5. ESP-12F supports development tools and provides reference programs for development environment; 6. Equipped with 4 relays rated for 5V, designed for switching output signals, suitable for controlling AC voltage loads; 7. On-board power indicator, 1 programmable LED, and relay status indicator; Power Supply: 4 channels: AC 90-250V / DC 7-30V / 5V; Serial Interface: GND, RX, TX, and 5V of ESP8266 are connected to GND, TX, RX, and 5V of external TTL serial module respectively; IO0 must be grounded during firmware download and disconnected afterward; Relay Output: NC: Normally Closed terminal connects to COM when relay is off, disconnects when relay is on; COM: Common terminal; NO: Normally Open terminal connects to COM when relay is on, disconnects when relay is off; Color: Green + Blue; Material: PCB + electronic components; Dimensions: 93 x 87mm; Package Includes: 1 x ESP8266 Wireless Wi-Fi Relay Module; Note: Light reflection and display differences may cause slight color variation between image and actual item. Measurement may vary by +/- 1-3cm.