Abstract: A ventilated enclosure for shielding electronic equipment from radio frequency energy having a minimum wavelength .lambda. which comprises a metal container forming a fully enclosed volume in which the electronic equipment is mounted. Cooling means, such as a fan, directs air through the volume to cool the equipment. The air enters and leaves the volume through an inlet duct and an outlet duct, respectively. Each duct forms a waveguide having a major cross-sectional dimension less than .lambda./2 and a length of the order of 2 .lambda. or greater.

Abstract: A solar heating system for heating a fluid with the infrared rays of the sun to provide a thermal supply to a building usable for heating the building and the domestic hot water supply thereto may have a solar heat absorbing panel for heating the fluid, which panel may be positioned away from the building, and a heated fluid storage tank with a conduit connection therebetween, wherein a mechanism may be connected to the solar heat absorbing panel for rotating this panel in two orthogonal planes of motion for aligning the panel with the direct rays of the sun including an electrical control circuit which may provide signals for positioning the panel preparatory to the beginning of each day and for changing the position of the panel when misalignment with the direct rays of sun occurs as well as for returning the panel to its initial beginning of day position when the temperature of the fluid within the storage tank reaches an upper limit.

Abstract: A door alarm apparatus, for signaling when a door has been jimmied or otherwise set ajar, is provided having a member which may be propped or otherwise jammed against a door, this door being in the normally closed position, for activating an alarm connected to this member where the member may be positioned in a fixed and predetermined spatial relationship to the threshold plate of the door whereby an anchoring component part of the may slidably mate with an anchoring component affixed to the threshold plate.

Abstract: An amplifier circuit having stable performance characteristics over a wide temperature range from approximately 0.degree. C up to as high as approximately 500.degree. C, such as might be encountered in a geothermal borehole. The amplifier utilizes ceramic vacuum tubes connected in directly coupled differential amplifier pairs having a common power supply and a cathode follower output stage. In an alternate embodiment, for operation up to 500.degree. C, positive and negative power supplies are utilized to provide improved gain characteristics, and all electrical connections are made by welding. Resistor elements in this version of the invention are specially heat treated to improve their stability with temperature.

Abstract: Data processing information storage and retrieval system having a memory. A number of modules are interconnected with the memory. Encode and decode modules operate in conjunction with the memory for compacting and expanding data. A revolve module in association with a delta module and a memory enable coded signals to be transferred into a number of unique but equivalent and related signals. A seed module enables the shortest of the equivalent signals to be located. A change module enables any one of the equivalent signals to be updated. An output module causes an equivalent signal to be converted back to the original signal representation. Pipe and brightness modules perform a discrimination function on stored information. The data processor includes programs which by unique means and methods structure and retrieve data from the data base. The retrieval may be based on an inexact match between events and entries of a request and the structured data base.

Abstract: A system for effecting the removal of ice from external surfaces of aircraft, and particularly from helicopter rotor blades, by the transmission of microwave electromagnetic energy into the ice so that it functions as a surface waveguide. The system includes a permanent surface waveguide with a dielectric constant close to that of ice, so that a composite surface waveguide is formed. The permanent surface waveguide is formed from a characteristically low-loss material, so that the microwave energy is dissipated as heat primarily in the ice layer, thereby very efficiently melting or heating the ice.

Abstract: A system for detecting ice on exterior surfaces of aircraft by transmitting a relatively low power microwave electromagnetic signal into a dielectric layer functioning as a surface waveguide, and monitoring the signals transmitted into and reflected from the waveguide. The waveguide includes a termination element which is mismatched with the waveguide impedance, resulting in partial or total reflection of the microwave energy from the remote end of the waveguide. As ice builds up on the surface waveguide, the impedance or reflection characteristics of the composite waveguide comprising the ice layer and the permanent surface waveguide give a reliable indication of the presence and location of the ice. The reflection characteristics are conventionally monitored utilizing a dual directional coupler and a reflectometer.

Abstract: Method and apparatus for scrambling and unscrambling television video and audio signals in a subscription television system in which program selections of subscribers are known at a central transmitting site, and control signals encoded into vertical blanking intervals of the video signals are addressed to receivers authorized to receive unscrambled transmissions, to selectively control unscrambling at those receivers. In an unscrambler at each subscriber's receiver, the control signals are decoded, and, if addressed to the particular subscriber's receiver, operate to enable or disable the unscrambler, or to frequently vary its mode of operation, thereby greatly increasing the security of the system and deterring viewing of scrambled transmissions. Video scrambling and unscrambling are effected by inversion of selected horizontal lines of a transmitted television picture, and a technique is disclosed for inversion of alternate groups of equal numbers of line.

Abstract: Method and apparatus for scrambling and unscrambling television video and audio signals in a subscription television system in which program selections of subscribers are known at a central transmitting site, and control signals encoded into vertical blanking intervals of the video signals are addressed to receivers authorized to receive unscrambled transmissions, to selectively control unscrambling at those receivers. In an unscrambler at each subscriber's receiver, the control signals are decoded, and, if addressed to the particular subscriber's receiver, operate to enable or disable the unscrambler, or to frequently vary its mode of operation, thereby greatly increasing the security of the system and deterring viewing of scrambled transmissions.

Abstract: Method and apparatus for scrambling and unscrambling television video and audio signals in a subscription television system in which program selections of subscribers are known at a central transmitting site, and control signals encoded into vertical blanking intervals of the video signals are addressed to receivers authorized to receive unscrambled transmissions, to selectively control unscrambling at those receivers. In an unscrambler at each subscriber's receiver, the control signals are decoded, and, if addressed to the particular subscriber's receiver, operate to enable or disable the unscrambler, or to frequently vary its mode of operation, thereby greatly increasing the security of the system and deterring viewing of scrambled transmissions.