and stable ESP-12f WiFi module on board, capacity 4mbyte flash. I/O port and UART program download port of WiFi module are all led out to facilitate secondary development. The power supply mode supports DC24 v. reset button and a programmable button for the onboard WiFi module. Esp-12f supports the use of eclipse / for LDE and other development tools, and provides reference programs under for development environment. On board 16 channel 24 V / 10 a relay, output switch signal, suitable for controlling the load whose working voltage is within AC 250 V / DC 30 v. On board power indicator, relay indicator module with LED. Two on-board shift registers 74HC595 control the relay switch. The 16 way relay is controlled by two 74HC595 cascades, so the corresponding control program of 595 is needed to open and close the relay. The reference program has been provided. Burning and writing port: GND, Rx, TX and 3.3V of esp8266 are respectively connected with GND, TX, RX and 3.3V of external TTL serial port module. IO0 needs to be connected with GND when downloading, and then disconnect IO0 and GND after downloading. Relay output terminal: NC: normally closed end, the relay is short circuited with com before closing and suspended after closing; COM: common end. No: normal start, the relay is suspended before closing, and it is short circuited with com after closing. Different batches, product appearance and color may be different, does not affect the use Colour:green Material:PCB type:5V Package Contents: 1 x Relay Module Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.