Abstract: A phase lock loop oscillator is provided with a voltage controlled oscillator which includes a current controlled oscillator and an input controller therefor that maintains the center frequency of the current controlled oscillator substantially constant irrespective of changes in the gain of the voltage controlled oscillator.

Abstract: A pressure monitoring system especially suitable for use with extra-corporeal circulation systems such as dialyzers, blood cell separators, oxygenators and the like, in which the internal system pressure must be monitored at one or more locations in the blood circuit, and appropriate warnings provided of pressure increases or decreases within defined limits. An initial pressure measuring cycle is provided and must be completed successfully before the main operating cycle of the overall system can begin. A pressure transducer provides signals to a digital closed-loop system which provides a suitable compensation during the initial or primary cycle and then holds that compensation value during the machine running cycle. Excursions of pressure beyond upper and lower limits of the stored reference or compensation value, in either direction, will cause the running cycle to terminate automatically.

Abstract: A digital pulse source generates a frequency analog of a desired velocity to which a d-c motor is accelerated. The acceleration circuit comprises a circuit means for converting a frequency analog signal to a frequency dependent direct voltage and a sawtooth voltage. A comparison circuit generates a motor drive signal having a duty cycle dependent on the relative voltage levels of the direct and sawtooth voltages. The comparative duty cycle of motor drive signal for two different velocities is regulated to be proportional to the square of the ratio of the two velocities.