A power control circuit for a three phase induction motor wherein power factors for the three phases are summed to provide a control signal, and this control signal is particularly filtered and then employed to control the duty cycle of each phase of input power to the motor. In a power factor type controller a signal is provided which initially blocks the application of the normal or "run" power factor command signal, and by means of a ramp signal generator, there is provided an increasing, with time, voltage in place of that command signal. This increase in voltage is of an amplitude and rate which will effect a graduated turn-on of the thyristor or thyristors of the motor circuit, effecting a full turn-on in a selected period of typically 5 to 30 seconds. A comparator examines the ramp voltage, and when the ramp voltage has risen sufficiently to effect a full turn-on of the thyristors and full motor operating speed, the comparator provides a signal which unblocks the normal power factor command signal, enabling the turn-on of a thyristor or thyristors to thereafter be determined by motor loading in a conventional manner. A trigger control circuit is provided for producing firing pulses for the thyristor of thyristor control system such as a power factor controller. The control circuit overcomes thyristor triggering problems involved with the current lag associated with controlling inductive loads and utilizes a phase difference signal, already present in the power factor controller, in deriving a signal for inhibiting generation of a firing pulse until no load current is flowing from the preceding half cycle and thereby ensuring that the thyristor is triggered on during each half cycle. PROSTHETIC OCCLUSIVE DEVICE FOR AN NASA Case No. MFS-25,740-1 Address inquiries to: Corresponding to U.S. Patent No. 4,408,597 Filed 4-23-82 Issued 10-11-83 An occlusive device is disclosed for surgical implant to occlude the lumen of an internal organ. The device includes a cuff A having a backing collar (10) and two isolated cuff chambers B and C. The fluid pressure of chamber B is regulated by a pump/valve reservoir unit E. Chamber C is unregulated in pressure but its fluid volume is adjusted by removing or adding fluid to a septum/ reservoir D by means of a hypodermic needle. Pressure changes are transmitted between the two cuff chambers via faying surfaces (12) and (14) which are sufficiently large in contact area and thin as to transmit pressure generally without attenuation. By adjusting the fluid volume of septum D, the operating pressure of the device may be adjusted to accommodate tubular organs of different diameter sizes as well as to compensate for changes in the organ following implant without re-operation. The invention is a television camera apparatus wherein bright objects are attenuated to fit within the dynamic range of the system, while dim objects are not. The apparatus receives linearly polarized light from an object scene, the light being passed by a beam splitter and focused on the output plane of a liquid crystal light valve. The light valve is oriented such that, with no excitation from the cathode ray tube, all light is rotated 90° and focused on the input plane of the video sensor. The light is then converted to an electrical signal, which is amplified by an amplifier and used to excite the CRT. The resulting image is collected and focused by lens onto a light valve which rotates the polarization vector of the light to an extent proportional to the light intensity from the CRT. The overall effect is to selectively attenuate the image pattern focused on the sensor. |