Abstract: A reservoir for re-usable cleaning fluid and filter for filtering fluid draining into the reservoir are positioned below an engine or supported engine component positioned at a cleaning zone. Cleaning fluid is delivered to the cleaning zone from the cleaning fluid held in the reservoir and the delivered cleaning fluid then drains into the reservoir (via the filter) from the cleaning zone above the reservoir. The cleaning fluid is re-circulated and filtered for continuous use.

Abstract: A satellite communications system comprises satellites 9A-C, earth stations 7A-E, user terminals 11 and controlling gateways 3 in the form of mobile satellite switching centers 5A-E. Access with a user terminal 11 may be gained to a terrestrial telephone system 1 by earth stations 7A-E contacting the satellites 9A-C and by the satellites contacting the user terminals 11. The satellites 9A-C periodically broadcast messages indicative of the earth station 7A-E with which they are instantly in contact. The user terminal 11 listens to and logs these broadcasts to keep a list of the relative number of times each earth station 7A-E can be heard. When calling into the system, the user terminal pages earth stations in descending order of number of entries in the log. When in contact, the user terminal 11 sends the log to the system. When subsequently trying to contact the user terminal 11, the system uses earth stations in descending order of number of entries on the log, last received from the user terminal.

Abstract: A terminal 44 44A 44B using standard navigational satellite 142 position determination to find its position on the surface of the earth 14, has its performance enhanced by being linked to a communications satellite system 10 38. In one variant, the communications satellite 10 broadcasts on each of a plurality of spot beams 30, each interactive with a different part of the earth, the broadcast indicating which navigational satellites 142 are accessible for a terminal within that beam 30. The terminal 44 44A 44B receives the broadcast and adjusts the navigational satellite receiver 174 to look for signals only from the nominated navigational satellites 142. In another variant, the communications satellite system 10 38 approximately measures the position of the terminal 44 44B and then informs the terminal 44 44B which navigational satellites are accessible from the terminal 44 44B, the navigational satellite receiver 174 again only looking for signals from the nominated navigational satellites 142.

Abstract: A satellite system and method comprises a satellite 10 induced to roll 46 and pitch 52 in its orbit 12 to keep antennae 34 36 pointing ever directly at the nadir 40 as the nadir moves over the surface of the earth 14. The satellite 10 has a yaw rotation 54 designed to keep the solar panels, which rotate only about one axis, ever pointing at ninety degrees to the direction of the sun 42 for maximum solar panel efficiency. The beam pattern of the antennae 34 36 is counter-rotated to oppose the yaw motion 54. Compensation for the season of the year is applied.

Abstract: DASD failures occurring on sector boundaries currently go undetected. While this sort of problem can occur at any time, it usually occurs when the program executing on the computer system's processor is operating on a multisector piece of data and periodically updating that information in auxiliary storage so that the copy in auxiliary storage is relatively up to date with the changes being made by the program. The storage management mechanism of the present invention solves the problem of sector boundary write failures by associating a sequence number with each piece of multisector data. Essentially, the sequence number becomes a property of the particular piece of data itself. When the mechanism retrieves the information from disk, it checks to make sure that all the sequence numbers match. If they do not, a data integrity problem has been detected.

Abstract: A circular magnetic demain device which includes bias magnets for applying a steady bias magnetic field in a direction normal to a major surface of the device's uniaxial magnetic layer; rotating magnetic field generating means for causing circular magnetic domains generated in the said layer to propagate within the layer along at least one path defined by a permeable circuit pattern formed on the said major surface, the generating means including two pairs of coils having their axes at right angles to each other and in the plane of the said major surface, one pair of coils being operable to provide an oscillating field which is unipolar and stops and starts at zero; and means for providing a holding magnetic field in the direction of the magnetic field provided by the said one pair of coils. In a preferred arrangement the holding magnetic field is provided by tilting the magnetic field of the bias magnets off-normal.