The figure displays the vacuum clutch system. Such a clutch utilizes the existing vacuum while in the engine manifold to operate the clutch. The vacuum clutch includes a reservoir, non-return valve, vacuum cylinder with piston, and solenoid valve.  A vehicle air conditioning compressor with a magnetic clutch. HowStuffWorks There are https://deanshugq.verybigblog.com/32308053/what-does-clutch-plate-mean