Abstract: A split tuning filter is disclosed in which at least two separate electrically interconnected filter sections mounted on a common circuit board are magnetically isolated through an isolation area defined by a pair of spaced isolation shields. A conductor interconnecting the two filter sections passes through the isolation area and has an external terminal connected thereto which allows each of the two filter sections to be independently tuned, with the isolation area minimizing the tuning impact of one filter section on the other. To further increase magnetic isolation, respective resonating capacitors provided in the filter sections have grounded plates perpendicularly interposed in the line of sight between primary tuning coils which are also respectively provided in the filter sections, with the grounded plates facing toward the isolation shields.

Abstract: A static inverter employing an inductor and an electrical gain element for intermittent assymetric energization of the inductor from a dc source is described. Reliable intermittent operation of the gain element, typically a power transistor, is achieved by use of three feedback windings which in response to saturation of a branch of the core of the inductor but before full core saturation, discontinue regenerative feedback and then apply degenerative feedback. This turn off mechanism protects the transistor from high current stresses. Passive means are provided such as a capacitor for momentarily storing the energy or diode means for coupling the energy back to the source or to the load to protect the transistor from the high voltage surge and the energy release when current flow in the inductor is interrupted. Energy stored in the capacitor may be used for transistor commutation.

Abstract: A smoke detector comprising a smoke detection cell of the ionization type and an electrical network providing for a.c. operation of the detection cell. The impedance of the detection cell changes in the presence of airborne combustion products and alters the operating frequency of the network. The frequency change is sensed to actuate an alarm. A.C. operation avoids the problem of d.c. instability in the high impedance detection cell circuit and simplifies sensing the electrical condition of the detection cell. The electrical network typically uses MOS-FET devices as the active circuit elements.

Abstract: The present invention relates to a regulated high voltage d.c. supply having an output voltage in the range of from 50 to 150 kilovolts such as is required for medical X-ray apparatus. The high voltage d.c. supply is constituted of a plurality of lower voltage d.c. to d.c. converter modules, whose output voltages are summed to produce the high voltage output. The converters are of a type which permits rapid activation and inactivation or "modulation". The modules are subjected to dynamic control to eliminate a.c. ripple, to regulate the high voltage output against supply line and load variations, and to turn the high voltage on and off in accurately timed intervals.

Abstract: A transformer designed to operate with a pair of power switching transistors in a d.c. to a.c. inverter is described. The transformer has an assembled core whose closed magnetic path is branched. A flux steering winding is used to ensure the prior saturation of a first branch associated with a regenerative feedback winding. Prior saturation of this branch reduces the forward drive on the switching transistors prior to full core saturation and avoids the consequent switching stresses on the transistors. The cores of the transformer are made from parts which abut at the branches so that both preformed power and preformed control windings may be used in assembling the transformer. The transformer may be assembled from conventional core configurations, and is thus of relatively low cost. A core arrangement is also disclosed in which the cross-section of the individual branches of the core may be adjusted.

Abstract: A static inverter is disclosed for d.c. to a.c. conversion comprising a pair of switching semiconductor devices and a power transformer having primary, secondary and control windings associated with a double apertured linear magnetic core. Each aperture partitions the core cross section in a localized region into two branches. The primary and secondary power windings encircle the full core, which has a closed magnetic path, while the control windings are associated with only a branch. Means are provided to cause one branch to saturate before the other branch and before full core saturation. Saturation of one branch is used to reduce the regenerative feedback and increase the degenerative feedback to provide an advance turn off, allowing charge stored in the switching device to dissipate prior to the end of each conduction period. This mode of the feedback control avoids full core saturation and avoids overstressing the switching devices that full core saturation would produce.

Abstract: An automatic gain control system applicable to a television receiver is described. Synchronizing pulses contained in the video detector output are sensed to obtain a measure of the signal strength. This is done by applying the detected output, containing the pulses, to a threshold circuit to produce current increments representative of the excess of said pulses over the threshold. The current increments thus obtained are then applied to a non-linear amplifier which, as a bi-directional source of current, supplies charging or discharging current, depending upon signal strength variation, to an integrating network to obtain a smoothed gain control voltage. The circuit is characterized by both fast attack and fast release and may be used with or without external gating. It is suitable for general AGC control in a television receiver which must be substantially immune to aircraft flutter.