Abstract: An instrument for use with a film containing a printed circuit layout. The instrument measures the area which is transparent to electromagnetic radiation of a characteristic wavelength so that the open area of the film and the average open area can be calculated and displayed. A source oriented in a direction perpendicular to the transport path emits radiation of the characteristic wavelength across a width of the film. A plurality of detecting devices responsive to the characteristic wavelength are arranged in a linear array in optical coordination with the source. Each detecting device detects radiation transmitted through an incremental area of the film and produces an output signal representative thereof. A detector circuit connected to receive the output signals repeatedly and sequentially provides digital area signals proportional to the amount of clear area within a respective incremental area of film. A microcomputer receives the area signals and computes the total clear area.

Abstract: An integrating photometer for measuring total exposures to ultraviolet radiation. The circuit for the photometer includes a threshold limiter to suppress operation of the integrator until the illumination level exceeds a predetermined threshold. A power saving circuit turns the photometer off when no illumination is received during a predetermined time interval.

Abstract: An improved audio-visual apparatus for projecting visual information segments carried by a transparency holder in an audio-visual cartridge, and for reproducing corresponding narrative and control information recorded on a movable storage medium carried by the cartridge. The apparatus includes an optical projector for projecting a selected one of the visual information segments onto a screen and a first drive mechanism for supporting the holder and selectively driving it to align specified visual segments with the optical projector. A second drive mechanism supporting the storage medium and selectively moving it independently of the holder to permit reproduction of recorded information is provided, and a playback device is mounted in operative relationship with the storage medium to produce signals corresponding to the stored information.

Abstract: The present invention comprises a short-pulse radar guidance tool which determines borehole-to-roof and borehole-to-floor distances along a coal seam by measuring the travel times of electromagnetic pulses transmitted from the tool and reflected back to a receiving antenna in the tool from the interface at the roof or floor of the coal seam. The tool includes a high frequency electromagnetic pulser, a directional transmitting antenna, a directional receiving antenna, a battery power source, and control circuitry for performing all control and transmitting/receiving functions at the tool location. Placement of the transmitting antenna at a point intermediate the control circuitry and the receiving antenna acts to reduce indirect electromagnetic coupling between the antennas. Circuit isolators are used to further attenuate RF crosstalk occuring between the control circuitry and the receiving antenna.