Pneumatic logic (Coanda-effect fluidics)

A jet of air entering a Y-shaped channel naturally attaches to one wall (the Coandă effect) and locks into that state by low-pressure recirculation. A small control jet on the opposite side provides enough momentum to switch the main jet to the other wall — bistable flip-flop behaviour with no moving parts. AND, OR, NOT, and NOR gates are realized by channel geometry; outputs fan out by splitting the attached jet. Developed in the early 1960s at the Harry Diamond Laboratories (Bowles, Gottron) and widely used in industrial control until PLCs displaced them. Inherently radiation-hardened (no electronics) and tolerant of dust and oil. MTBFs of 25,000–50,000 hours reported. Speed: milliseconds per gate switching (air transit time). Capacity: arbitrary boolean circuits; industrial systems ran thousands of gates.