An impression tray for the lower mouth of an edentulous patient comprises a downwardly opening arch-shaped trough for holding impression material in contact with the gum tissue overlying the patient's mandible. The trough has a downwardly extending buccal flange along its outer side, and a downwardly extending lingual retaining wall along its inner side. The lingual retaining wall extends below the bottom edge of the buccal flange continuously for the length of the mylohyoid ridge in the patient...

Damaged, flexible vinyl materials, such as automobile seats and tops, are repaired by a welding compound which is grained and colored to match the base material. The damaged section of the base material is prepared by removing frayed edges and the like to obtain a clean, sharp periphery. The base material is cleaned by a solvent to ensure adhesion or fusion of the welding compound with it. The welding compound is a vinyl compound which has a relatively high tensile strength and relatively low fu...

There is described an apparatus for monitoring the contents of any selected location in the main memory of a computer. The contents of an addressed location in memory is read out periodically and compared with the prior contents of the same memory location. On sensing a change in the contents of the memory location, operation of the computer is halted.

A loop extension unit for transmission circuits for increasing the central switching office to subscriber station range. The unit provides dial pulse repeating, transmission of ringing signals from whatever source provided and other supervisory signalling. Interruption of ringing is controlled by the unit by detection of an off-hook condition at the subscriber location with the ringing circuit locked out during completion of the subscriber loop between the central office and the station. DC isol...

A relay mount includes a case for a relay, ears projecting away from both sides of the case, connector pins extending from the case above the plane of the ears, and a mounting track with spaced-apart elongated grooves in which the ears make a sliding and releasable fit.

A double focusing mass spectrometer utilizing an electric and a magnetic analyzing sector in tandem provided with a mechanically adjustable magnetic sector. Optimum focusing of the instrument is obtained by translational and rotational adjustments of the magnetic sector.

A metal strip that fits along the front edge of a shelf for reinforcing the shelf edge and also providing a place to hang conventional coat hangers is roll formed from sheet metal. A generally T-shaped end clip at each end is fittable over the edge bar for holding it in place and also for length adjustment. The end clip has a fastener receiving aperture on the cross bar of the T for accommodating a nail, screw or the like into the shelf end nailing strip.

A technique particularly useful for measuring the flying characteristics of a magnetic recording head on an air bearing adjacent a rotating disk is described. According to this technique one of a plurality of magnetic transducers mounted in the moving disk records a line of signals of known amplitude and wavelength on a magnetic recording surface placed on the recording head being evaluated. The signal amplitude is read from this line of recorded signals as the disk rotates, and the relative spa...

A high-speed inexpensive magnetic tape duplicator is provided which is capable, for example, of duplicating a program recorded on a master magnetic tape simultaneously on a plurality of cassette-type magnetic tape cartridges preloaded with magnetic tape, and the like. The apparatus of the invention is controlled so that all tapes quickly come up to speed in order that maximum use may be made of all the tapes in the various cassettes. This minimizes the beginning portion of poor recording quality...

In a magnetic tape transport, an electromagnetic transducer assembly is positioned adjacent a capstan tape drive. Magnetic tape wraps around the capstan and the capstan moves the tape past the transducer. Fluid pressure applies a force on the tape at a position in between the transducer assembly and capstan which forces the tape away from the capstan toward the transducer assembly.