Push Button (Tactile Switch)Momentary SPST-NO tactile switch

A push button is a momentary switch: its contacts close only while the plunger is held down, and a spring opens them again on release. Tactile switches like the Omron B3F add a snap dome, so the press is felt as a click at a defined force. The B3F is made for logic signals, not loads: 1–50 mA at 3–24 V DC (resistive). Closed, the contact measures at most 100 mΩ at first; open, more than 100 MΩ. A microcontroller reads it through a pull-up resistor, and because the contacts bounce for up to 5 ms the program or an RC filter must ignore the first few milliseconds after each edge. This page covers the 6 × 6 mm B3F-1000 and the 12 × 12 mm B3F-4000, the two push buttons in ProTech. Each has four leads but only two contacts: the two leads joined across the body form terminal 1, the other two terminal 2. The page, ProTech and the KiCad footprints number them 1 and 2.