It provides numbers from 0 to 9, and A B C D, as well as standard stars (*) and hash symbols (#) | Keypad is a combination of row and column circuits. | The keyboard matrix allows you to quickly add controls to your electronic projects. Easy to communicate with any microcontroller. | There is a switch connecting each row and column. So the combinations of rows and columns makes up the 16 inputs. | Application: Password security system, Generating external interrupt, Automatic Gate Keypad Lock.