4×4 Flat Matrix Keypad

This keypad consists of 4 rows x 4 columns of buttons. It is ultra-thin that it provides a useful human interface component for microcontroller projects.
Convenient adhesive backing provides a simple way to mount the keypad in a variety of applications, such as menu selection, security systems, data entry for embedded systems and so on.
The buttons on a keypad are arranged in rows and columns. A 3X4 keypad has 4 rows and 3 columns, and a 4X4 keypad has 4 rows and 4 columns. Beneath each key is a membrane switch.
Each switch in a row is connected to the other switches in the row by a conductive trace underneath the pad. Each switch in a column is connected the same way, one side of the switch is connected to all of the other switches in that column by a conductive trace.