Inertia starter reducing film drive at sound head - reduces acceleration time drive requirement and noise

The film-transport mechanism at the sound-recording station of a cine camera is moved by a belt-driven heavy rotor. In starting it up, it is desired to abbreviate the acceleration time of the transport roller. This is done by first accelerating the massive rotor to its full speed, and only then coupling the comparatively light transport mechanism to it. The coupling is made by magnetising the intertial rotor by a solenoid, so that it attracts and holds a ferro-magnetic disc which slides on pegs fixed in the transports roller flange. The inertial rotor has two ferro-magnetic sections separted by a non-magnetic. ring.