Abstract: Described are chairs having a seat with a sitting location above the floor, a base that sits on a floor, a lift connecting the seat and the base, the lift capable of moving the seat up and down from the sitting location to a lower location at the floor, and a control system operating the lift. The control system allows an occupant of the chair to move the seat between its sitting location and the lower location at the floor to enable the occupant to pick up or place an item on the floor while sitting in the chair and thereafter to move the seat upwardly.

Abstract: A work platform for use in performing maintenance while supported on an overhead crane. The work platform is particularly useful for performing maintenance on an overhead cranes located in areas where normal lifting equipment and/or scaffolding cannot easily access the overhead crane. However, the work platform is also useful for performing maintenance on equipment and/or structures in the vicinity of overhead cranes, and on overhead cranes located in areas without accessibility problems. The work platform is hoisted for placement on the support structure of the overhead crane by hoist apparatus of the overhead crane. When positioned, the work platform may be fully supported on the support structure of the overhead crane.

Abstract: A power line communication system and signaling protocol is usable for quick dimming of an electronic ballast. An encoding circuit transmits message frames having encoded control signals across a AC power line. Each of a first set of frames includes a bit pattern corresponding to a lighting zone, and a second set of frames includes hamming-encoded bit patterns corresponding to respective hexadecimal digits of a dimming level for the lighting zone. A ballast in a first (quick-dim) configuration detects the second set of frames, decodes the hamming-encoded digits and immediately adjusts the ballast output to the desired power level. The ballast in a second (normal) configuration determines the desired power level based on a pattern density in the first set of frames, and adjusts the output current of the ballast accordingly. If the ballast of the first configuration fails to detect the second set of frames, it defaults to pattern density recognition.

Abstract: A work platform for use in performing maintenance while supported on an overhead crane. The work platform is particularly useful for performing maintenance on an overhead cranes located in areas where normal lifting equipment and/or scaffolding cannot easily access the overhead crane. However, the work platform is also useful for performing maintenance on equipment and/or structures in the vicinity of overhead cranes, and on overhead cranes located in areas without accessibility problems. The work platform is hoisted for placement on the support structure of the overhead crane by hoist apparatus of the overhead crane. When positioned, the work platform may be fully supported on the support structure of the overhead crane.

Abstract: A system and method is provided for encoding and decoding control signals to an electronic ballast. An encoding circuit is effective to transmit encoded control signals across an AC power line comprising patterns of energy bursts at zero crossings of an AC signal. Eight zero crossings define a set, five specific patterns of energy bursts within a set define distinct symbols, each defined symbol selected such that a Hamming distance between each symbol is greater than three. Four symbols correspond to a first logic condition and one symbol corresponds to a second logic condition. Each received symbol is sequentially associated with a distinct control channel having one or more control parameters. A receiving circuit in the ballast is effective to decode symbols with single-bit error correction by comparing received symbols to defined symbols and determining which symbol is a smallest Hamming distance from a received symbol.

Abstract: A work platform for use in performing maintenance while supported on an overhead crane. The work platform is particularly useful for performing maintenance on overhead cranes located in areas where normal lifting equipment and/or scaffolding cannot easily access the overhead crane. However, the work platform is also useful for performing maintenance on equipment and/or structures in the vicinity of overhead cranes, and on overhead cranes located in areas without accessibility problems. The work platform is hoisted for placement on support structure of the overhead crane by hoist apparatus of the overhead crane. When positioned, the work platform may be fully supported on the support structure of the overhead crane.

Abstract: A motion picture camera having a capability of recording sound on film simultaneously as the film passes the image recording station, is improved by the use of a single drive motor which powers film moving mechanisms at both stations. A novel speed change assembly is used to vary the drive of the film through the image recording station in response to the condition of a film loop between the stations as detected by a mechanical sensor which controls the speed change assembly.