Abstract: A position sensor for sensing the angular position of an oscillatory member includes a magnetic element which is permanently magnetized in a predetermined direction and is mounted as a unitary structural part of the oscillatory member for oscillatory movement therewith. A Hall plate sensor is positioned adjacent the magnetic element to detect changes in the magnetic field presented thereto by changes in position of the magnetic element. When the magnetic element is oscillated with the transducer, the magnetic field presented to the Hall plate is varied accordingly. This, in turn, produces an electrical signal as an output of the Hall plate which is a function of the instantaneous position of the magnetic element and hence of the oscillatory transducer. That electrical signal may then be used to produce synchronization signals for the imaging apparatus.

Abstract: A housing for an electroacoustic transducer includes a filling or access port for introducing an inert liquid into the chamber defined by the housing. The access port includes a bubble trap and a vent for extracting gaseous bubbles from the fluid fill. The structure of the access port also comprises a substantially zero spring pressure expansion cavity for the fluid.

Abstract: A dual reel hub assembly for coaxially mounting two independently rotatable confronting reels on an axially inward hub structure and an axially outward hub structure, respectively. The inward and outward hub structures are mounted on a common central spindle with the inward hub structure being freely rotatable while the outward hub structure is fixedly attached to the spindle and spaced from the inward hub structure. Each hub structure includes a reel support shell for supporting an inner surface of an axial opening in a reel. A plurality of radially outwardly extending key pins are aligned parallel to the spindle axis on each reel support shell to mate with one of a plurality of keyways on the inner surface of the axial reel opening. A rotatable locking ring on each hub structure is dimensioned to pass through the axial reel opening and has radially outwardly projecting locking fingers dimensioned to pass through the keyways and equal in number thereto.

Abstract: A slack tape loader for a tape transport apparatus has a signal generator selectively energized by a tape loading control switch to produce an enabling signal for a reel motor control servo circuit. The enabling signal has a duration which will energize the reel motor control servo for a short period of time to load the slack tape on tape storage reels. Concurrently, the tape transport is operative to detect a tensioned state of the tape. The enabling signal is recurrently produced by the signal generator in response to the tape loading control switch until the desired tape tension is detected by a tape tension sensing means to produce an output signal for disabling the signal generator.