Abstract: A motion detector of the space surveillance type wherein an elongate box has parallel walls and an aperture opening toward sensors, and a pair of upwardly divergent reflectors is provided for at least one of the two sensing field planes, the reflectors making an angle of 20.degree. or less with each other.

Abstract: A motion detector with at least one sensor to receive electromagnetic radiation, in particular in the infrared range, from a radiation receiver surrounding a monitored object at least partially, and with an evaluating circuit to trigger a control signal upon a change in the intensity of the radiation. A motion detector of this type may be manufactured cost effectively and is suitable for the reception of electromagnetic radiation from an angular range of up to 360.degree. of closed fields of sensitivity because the closed field or fields of sensitivity are formed by the shape of the sensor or sensors.

Abstract: A motion detector responsive to infrared radiation, e.g. for use in burglar-alarm installations, comprises a pair of juxtaposed sensors monitoring adjacent fields of view of a space to be surveyed, giving rise to output signals of opposite polarity upon detecting a disturbance in their respective fields. These output signals are fed to an evaluator comprising two complementary transistors with interconnected emitters and interconnected bases whose junctions are separated by a resistive branch of an RC network, the emitter junction receiving the output signals while the base junction is capacitively coupled to ground or some other point of fixed potential. The collectors of these transistors, energized via respective resistors from opposite terminals of a d-c supply, are connected to respective timers working into a common AND gate which triggers an alarm when an alternation of output signals from the two sensors renders the timers conductive for overlapping periods.

Abstract: A motion detector responsive for infrared radiation, e.g. to use in burglar-alarm installations, comprises an elongate frustopyramidal box with an entrance opening at one end, a concave mirror at the opposite end and four flat, internally reflecting longitudinal walls, two of them converging toward the entrance end on opposite sides of a plane of symmetry with which they include an angle between about 8.degree. and 15.degree.. A pyroelectric radiation sensor near the entrance end, lying in the vicinity of the focal point of the concave mirror, is disposed for illumination by beams of parallel rays in a limited number of fields of view; these beams approach the entrance end at different azimuthal angles, included with the preferably vertical plane of symmetry, but occupy closely adjoining regions inside the box. A planar deflector at the entrance end, bisected by the plane of symmetry, also establishes a limited number of elevational angles for the beams focused upon the radiation sensor.