and stable ESP-12f WiFi module on board, capacity 4mbyte flash. I/O port and UART 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 / 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 of 595 is needed to and the relay. The reference has been provided. Burning and writing port: GND, , TX and 3.3V of esp8266 are respectively connected with GND, TX, 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 closing and suspended after closing; : common end. No: normal start, the relay is suspended closing, and it is short circuited with after closing. Different batches, product appearance and color may be different, does not affect the use Colour:green Material:PCB type:24V Package Contents: 1 x Relay Module