Two working mode : Mode 1:cellphone carry on wifi module directly Mode 2: cellphone and wifi module carry on router Additional function :work as USB module when remove ESP-01 module Transmission distance: (1) the open environment, when the mobile phone carrying on the WIFI module ,maximum transmission distance is 100 m; (2), when the WiFI module and cell phone carrying on the router at the same time, the signal transmission distance depends on router signal Use the Smartconfig technology to complete the configuration of the account and password of the esp-01 WIFI module on the mobile APP. The configured account and password will be memorized after power off The board contains 12V,10A/250V AC 10A/30V DC relay, which can continuously 100,000 , with the protection of diode current and short response time. With mode option and working statue LED indicator.With 4 isolator and strong anti interference .Reserved UART debug interface and MCU download port for Interface on board:IN+,IN-:5V voltage input 5V,GND,TX,:UART serial port PIN SWIM,PIN8,NRST:reserved MCU download port Button S1:change mode,default mode is mode 1 Button S2:reset LED D1/D2/D3/D4(red ):relay working LED,LED on when relay is on LED D7(red ):indicator for mode 1 LED D5(blue):indicator for mode 2 LED D6(green ):work statue indicator ,exact details as : When extinguished, it is being configured or disconnected from the router. 0.5s fast blinking represents cellphone app is configuring WIFI account and password for ESP-01 module 2S slow blinking to configure finished ,and wait for connection with cellphone by LED always on represents connections with mobile phone successfully Connection for reserved two cap jumper: Generally ,insert to bottom ,that is to RX1,TX to TX1 .Insert to upper ,when use it as USB module COM1 COM2 COM3 COM4:Common terminal NC1 NC2 NC3 NC4:normal NO1 NO2 NO3 NO4:normal open Control for relay (hex ): Open relay 1:A0 01 01 A2 relay 1:A0 01 00 A1 Open relay 2:A0 02 01 A3 relay 2:A0 02 00 A2 Open relay 3:A0 03 01 A4 relay 3:A0 03 00 A3 Open relay 4:A0 04 01 A5 relay 4:A0 04 00 A4 Colour:Blue Material:PCB Size:60*63mm Package Contents: 1x 12V ESP8266 Four Ways Wifi Relay Switch Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.