Abstract: A method and apparatus for using a magnetic field generated by a thruster magnet to control electron current emitted by a cathode assembly. The magnetic field reduces leakage current drawn by an inactive anode by producing a magnetic field in proximity to the inactive anode. This magnetic field increases the impedance to the anode for electron current which is produced in the cathode assembly. This reduction in leakage current reduces the amount of electron current produced by the cathode assembly. This control system can be implemented by connecting all thruster anodes and cathodes in parallel to an anode power supply.

Abstract: A single power control circuit selectively distributes power from a power supply to cathode heater, cathode keeper and thruster magnets of a thruster. The power control circuit utilizes a plurality of switching devices to direct power to one or more of the heater, keeper, and magnet components.

Abstract: There is disclosed an arcjet starter for igniting and sustaining an electric arc in an arcjet thruster. The arcjet starter is capable of delivering a short duration, high voltage pulse for igniting the arc and then providing a continuous low voltage, high amperage current for sustaining the arc. The starter has two separate magnetics, one for initiating breakdown in the arcjet and another for sustaining breakdown during steady state operation.

Abstract: A control for an electroluminescent panel which utilizes a resonant switch, preferably comprising two silicon-controlled rectifiers mounted anti-parallel. The amplitude of the output voltage of the resonant switch going the panel is changed by changing the voltage at which the switch is turned on. The voltage in the panel is resonated from one polarity through zero to the opposite polarity.

Abstract: In a multiprocessor system, a plurality of data processors are each equipped with a local, level 1, cache and have access to a main memory through memory access circuit having a level 2 cache and a single register arbiter. The single register includes a primary queue defining priority of requests from the plurality of processors and a secondary queue defining processor requiring access to main memory. The register contains one position for each of the processors served and employs a pointer for demarcation between the primary and secondary queues. When a request is detected, the highest priority processor in the primary queue is served and when the requested memory address is in the level 2 cache, it will be retrieved and the identity of the served processor will be moved to the low end of the primary queue as defined by the pointer.

Abstract: This invention provides a self-contained user-actuated breathing device of the type used by industry and firefighters to protect against toxic atmospheres, which includes means for reducing user respiratory fatigue during periods of heavy physical exertion or stress, while maintaining facepiece pressure in a preselected narrow range of positive pressures relative to atmospheric to protect the user from ingress of toxic outside atmospheres. The invention includes a feedback mechanism responsive to facepiece pressure which actuates a supplemental second inlet air flow path to the facepiece during periods of high user demand. Also provided is a novel nonlinear expiration valve mechanism which is responsive to facepiece pressure to prevent facepiece pressure from exceeding a preselected positive level, thereby minimizing user expiratory fatigue which is commonly associated with such devices.