Components: Blue 16x2 1602 lcd display + I2C serial interface backpack; 1602 lcd screen can display 2-lines x 16-characters with built-in industry standard HD44780 equivalent LCD controller. Default Address: 0x27 for PCF8574T chip; 0x3F for PCF8574AT chip; please check which chip you have on i2c interface. (Before you upload the code to the control board, please download the LiquidCrystal_I2C library) Four Pins: VCC, GND,SDL and SCA used for connecting Dupont Line or IIC dedicated cable. Compatibility: used for connecting Ar-duino and Raspberry pi and it can be used to display real time clock, temperature, humidity etc. (A potentiometer is also necessary to adjust the contrast. Working Voltage: Only 5V ) Wide Application: Commonly used in copiers, fax machines, laser printers, industrial test equipment and networking equipment such as routers and storage devices.