Introduction
Reducing valves are linear motion type valves. A reducing valve supplies a constant fixed pressure to the discharge side of the valve. Pressure is supplied to the inlet where it either passes through the valve directly or is reduced to a pre-determined pressure.
Additional Resources
https://en.wikipedia.org/wiki/Pressure_regulator
https://www.bermad.com.au/how-to/how-does-a-pressure-reducing-valve-work