Abstract: A threshold circuit for signal receiving equipment, particularly optical signals travelling to or from a rapidly flying object comprises a threshold determining device having an input accepting signal and noise pulses and an output emitting transmitted pulses which correspond to the signal and noise pulses that pass the threshold unit. Control circuits determine the threshold that is employed in response to the received signal and noise pulses. If the received signal and noise pulses have a relatively low amplitude, a relatively low predetermined threshold is employed. If the received noise and/or signal pulses increase in amplitude for a sufficient length of time, the control circuits respond by raising the threshold.

Abstract: A system for determining the deviation of an object from a reference line, in particular for determining the deviation of a guided missile from a sight line extending from the missile launcher to a target, comprises a transmitter assembly at the origin of the reference line and a receiver assembly in the object. The transmitter assembly includes a radiation beam projecting device emitting a radiation beam in the direction of the reference line, this radiation beam being such that in planes perpendicular to the reference line it produces a radiation pattern composed of two elongated narrow radiation strips, which are mutually perpendicular and sweep alternatingly and periodically with a predetermined sweeping frequency over the reference line in directions at right angles to their respective longitudinal directions.