Abstract: A deck structure and fence for above ground swimming pools, with the deck being supported at its inner peripheral end on the seat rest mounted on top of the swimming pool side wall. The deck is comprised of a plurality of platform sections of predetermined size and shape, and by adjusting the distance by which the deck section inner ends overhang the seat rest, the same group of deck sections may be used with round or oval swimming pools having arcuate side walls within a predetermined range of diameters. The outer end of the deck is supported on upstanding posts having lock tabs at both ends. Openings formed through the lock tabs define hinge lines at predetermined locations which cause the lock tabs to be tensioned and prestressed as they are bent into locking engagement with deck frame members and ground support plates through mating apertures therein. A deck fence is held together by a double lock tab arrangement through which the fence top rails are securely interlocked with upright fence posts.

Abstract: A pump and filter assembly suitable for circulating and filtering swimming-pool water is provided with a normally closed air-injection valve to aerate water flowing into a filtration element in the filter. When the exterior surfaces of the element become covered with dirt or filter cake, the air-injection valve and an auxiliary filter outlet are opened. Air aspirated through the valve into the filter inlet water stream causes a churning cleaning action which dislodges the dirt, and the debris-laden water is discharged through the auxiliary outlet without passing through the element.

Abstract: Multiplexed seismic data representing a plurality of seismic channels intensity modulates each sweep of the electron beam of a cathode-ray tube. Each successive sweep of the electron beam is photographically reproduced on a rotating drum plotter to provide a seismic record section. The modulation of the cathode-ray tube is further controlled to provide for various seismic trace presentations on the record section, including wiggle traces, variable area traces, wiggle-variable area traces, and symmetrical-variable area traces.

Abstract: Multiplexed seismic data representing a plurality of seismic channels intensity modulates each sweep of the electron beam of a cathode-ray tube. Each successive sweep of the electron beam is photographically reproduced on a rotating drum plotter to provide a seismic record section. The sweep signal for controlling the electron beam is automatically gain controlled so that the number of seismic traces per inch remains constant.

Abstract: An apparatus for plotting information, e.g., seismic data, onto a continuous sheet of a recording medium, e.g., photographic film. The film travels from a supply reel, over an advance roller, across a flat exposure surface, and onto a takeup roller. Torque motors apply equal but opposite torques to the supply reel and the takeup reel to maintain the film in tension to insure that the film will lie flat on the exposure surface during the plotting operation. A stepping motor rotates advance roller to move the film a precise amount across the exposure surface at desired times during the plotting operation. A camera, e.g., cathode ray tube, which receives data and projects it onto the film on the exposure surface, is mounted on a carriage which is swept back and forth across the exposure surface by means of a lead screw driven by a precision stepping motor.

Abstract: A skimmer filter and pumping unit for an above-ground swimming pool including portable pools in which a centrifugal pump is mounted on a base beside the pool. A cartridge-type filter unit having a cylindrical housing is supported from the base above the pump with the pump and cylindrical housing aligned along a common vertical axis. A skimmer unit is mounted on top of the filter unit and has an opening in the side adapted to open through the side of the pool adjacent the top of the pool when the base is resting on the ground. Water moves directly through the skimmer unit down through the filter into the pump, the pump dishcarge being connected back through the side of the pool below the skimmer.

Abstract: Apparatus for indicating when a swimming pool filter needs to be cleaned, which comprises a flexible diaphragm covering an opening in the conduit on the inlet side of a pool filter and a housing covering the diaphragm with a movable piston member inside the housing and engaging the surface of the diaphragm. Spring means urges the piston against the diaphragm to counteract pressure of water in the conduit against the diaphragm. A movable flag is operated by the piston means to indicate through a window in the housing when the piston has moved a predetermined distance.