The determine displays the vacuum clutch mechanism. This type of clutch uses the existing vacuum in the motor manifold to work the clutch. The vacuum clutch contains a reservoir, non-return valve, vacuum cylinder with piston, and solenoid valve.  A car or truck air conditioning compressor by using a magnetic clutch. https://clutch-kereta75307.blogproducer.com/39937845/clutch-plate-an-overview