Beaulieu 4008 series cameras use the transistorized electronic speed regulation. As seen on the above diagram, a generator connected to the motor shaft is in communication with the phase inverter, and so on.
Transistorized regulation systems allow a motor to withstand large speed variations without loss of power while ensuring perfect rotational stabilization at all possible r.p.m.
Should the motor’s speed drop, the voltage delivered by the generator drops; at this moment a Darlington amplifier feeds the motor a high amperage, thus allowing motor to resume its normal speed. This feedback mechanism naturally acts the other way, should the motor’s speed increase, it is reversed. So, the fixed speed is achieved.
These regulation phenomena occur within a few thousandths of a second. They are permanently effective, thus ensuring perfectly speed stabilization.
Another advantage is that a very wide range of filming speeds becomes available, both where slow and high speeds are concerned and this continuously, all intermediate speeds being usable even in the middle of filming.