Abstract: To avoid collision between aircraft flying in the same general area, each aircraft has individually assigned to it a transmission interval or time slot for sending out data relating to its altitude, course and speed, successive time slots being distinguished by different carrier frequencies. From the received data, each aircraft determines the relative positions and speeds of other aircraft communicating with it. Upon finding itself on a collision or near-collision course with another aircraft, an aircraft initiates an accelerated exchange of information with that other aircraft to determine the passing distance thereof and, if necessary, to take collision-avoiding action.

Abstract: The herein disclosed synchronization extractor is designed to recover a train of useful pulses of given recurrence period T from an input signal containing both useful pulses and parasitic pulses. Each period T is divided into n sampling intervals of a duration less than or equal to that of the pulses. The pulses present in the several intervals are respectively counted by n reversible counters. Backward-counting pulses, having a recurrence period which is greater than the period T but less than the recurrence periods of the parasitic pulses, are applied to the counters simultaneously. The useful pulses are collected from that counter in which the mean rate of the forward-counting pulses exceeds that of the backward-counting pulses.