Abstract: A discharge lamp with high intensity and high local stability is disclosed, which is suitable for use as a light source in a visibility meter. A light receiver also suitable for use in a visibility meter is disclosed. The discharge lamp has a discrete anode chamber and a discrete cathode chamber which are both filled with gas and which are interconnected via a capillary tube. One end of the capillary tube is adjacent a cathode located within the cathode chamber, while the other end of the capillary tube projects forwardly of a region in which the anode is adjacent the capillary tube. Plasma is confined within the capillary tube, resulting in high local stability and high intensity light output. The light receiver utilizes a photosensitive element and an electrical filter which is so designed that response of the light receiver is calibrated to include or coincide with that portion of the visible light spectrum which carries maximum energy.

Abstract: An improvement to a laser ceilometer and like instruments comprises a laser diode array which includes a plurality of laser diodes, and an array driver driving the laser diode array in accordance with commands from a microprocessor. The laser diodes are GaAs diodes. By utilizing the improvement, service life and reliability of the ceilometer are both increased.

Abstract: Two embodiments of the visibility meter are disclosed. In the first embodiment, light transmitted from the light transmitter and light received by the light receiver is propagated in a conical beam. The beams are so oriented that they include an obtuse angle. In the first embodiment, a partition blocks all direct transmission of light from the light transmitter to the light receiver. In the second embodiment, direct transmission of light from the light transmitter to the light receiver takes place through the partition, but is limited to a predetermined level.

Abstract: A laser ceilometer emits a pulsed and narrow beam of visible or invisible laser radiation directly vertically upwards. The effective power level of the emitted radiation is lower, but only by a safety margin, than can result in eye damage to naked-eye observers viewing the directly emitted beam directly, but is higher than the power level resulting in eye damage to an observer viewing the directly emitted beam directly through a telescope having an objective of 80 mm diameter. When, in the course of cleaning or adjustment work, or for any reason, the ceilometer is tilted from its normal, vertically upwards aimed orientation towards a horizontally aimed orientation, by an angle of more than 10.degree.

Abstract: In a ceilometric system, light pulses are emitted from a transmitter towards overhead clouds and reflected back down towards a receiver which generates a photodetector signal transmitted by a gate whose gating interval is shifted in time relative to the light-pulse emission instant to define successive range steps. During each dwell at a particular gating interval and range step, the photodetector signal is integrated to develop an integral signal for that range step. The integral signal for each range step is digitalized and stored in a digital storage circuit, ordered in correspondence to the sequence of the range steps. A microprocessor searches for the largest one of the stored integral signals and derives a ceilometric indication in dependence thereon.

Abstract: An onboard power supply and metering unit is connected, via an overboard cable e.g., 1000 meters long, to an underwater light-pulse projecting unit and a fluoroescence-sensing receiver unit. The operating power is transmitted to the underwater units by an onboard constant-current source, instead of a voltage source. Likewise, the output signal of the receiver unit is transmitted through the cable in the form of a current, not a voltage. The current of the receiver's photodiode is integrated, the peak value of the integral determined and held, this held value logarithmized, the logarithmized value sampled and held, and the held voltage converted to a current constituting the output signal. The offset of the peak detector and the input stage of the log amplifier are balanced automatically, by a balancing signal applied during pulse measurements, but derived between pulse measurements.

Abstract: An arrangement for determining the density of natural fog in the atmosphere in which a spark lamp serving also as a flashing beacon projects a beam of light composed of consecutive pulses through the fog laden atmosphere so as to scatter part of the light to thus form consecutive pulses of scattered light in a defined region of the path of the light beam, the intensity of which is proportional to the density of the fog in this region, and in which light pulse receiver means are constructed and arranged relative to said region so as to receive only the scattered light pulses which are measured by the receiver means to thereby indicate the density of fog in the aforementioned region.

Abstract: A high frequency oscillator is pulsed on and off to create at least a first and second pulse to be applied by inductive heating to a steel tool which has not previously been heat treated. The pulse width, amplitude and interval between pulses are adjusted for a given alloy and then kept constant during the production run. A Hartley oscillator with a frequency above 10 MHz is utilized and the pulses have pulse widths of less than 100 milliseconds.

Abstract: An antenna receives electromagnetic radiation and furnishes a corresponding signal which after differentiation sets a first monostable multivibrator whose output lasts for several microseconds. A photodiode receives light signals. If the light signals are received within the time that the first monostable multivibrator is set, the generation of an alarm is inhibited, since substantially simultaneous reception of electromagnetic and light signals indicates either atmospheric disturbance or conventional weapons. In the absence of an inhibit signal, a second multivibrator is set for several milliseconds at the end of the setting of the first multivibrator. Any light received while the second multivibrator is set results in the furnishing of an alarm.

Abstract: An upright tubular housing has a lower end portion connectable to the ground, and an upper end portion. Arrangements for emitting and/or receiving light pulses are mounted in the lower end portion of the housing and a deflecting mirror is mounted in the upper end portion for deflecting the light pulses between a vertical and a substantially horizontal path. A break-away zone is formed in the lower end portion in the region where the same is connectable to the ground so that in the event of collision with an aircraft the housing will break away at this zone to thereby reduce the collision danger to the aircraft.