1. On-board mature and stable ESP-12F Wi-Fi module with 4MB flash memory; 2. I/O port of the Wi-Fi module and UART download port are fully accessible for 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 environments; 6. Equipped with 4 relays rated for 5V, suitable for switching output signals and controlling AC voltage loads; 7. On-board power indicator, 1 programmable LED, and relay status indicators; Power Supply: 4 channels AC 90-250V / DC 7-30V / 5V; UART Interface: GND, RX, TX, and 5V of ESP8266 connected to corresponding pins of external TTL serial module. IO0 must be grounded during firmware upload and disconnected afterward; Relay Output: NC Normally Closed, connected to COM when relay is off; COM Common terminal; NO Normally Open, connected to COM when relay is on; Color: Green and Blue; Material: PCB and electronic components; Size: 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.