The figure reveals the vacuum clutch system. This kind of clutch works by using the present vacuum within the engine manifold to work the clutch. The vacuum clutch consists of a reservoir, non-return valve, vacuum cylinder with piston, and solenoid valve.  In the event the clutch is engaged (clutch pedal https://clutchkereta97429.blogoxo.com/33179149/details-fiction-and-clutch-kereta