Abstract: 1. A radio pulse signalling system comprising, in combination:Means for generating a first time base consisting of a finite number of regularly time-spaced pulse signals;First means for forming a pulse code group from said time base signal in accordance with a preselected pattern, said pulse code group always including an initial starting pulse;Means for transmitting a pulsed radio wave corresponding to said pulse code group;Means for receiving said pulsed radio wave at a remote point;Means, actuated by the initial starting pulse in said received wave, for generating a second time base corresponding to said first time base; andSecond means for forming a pulse code group corresponding to the transmitted pulse code group from said second time base signal.

Abstract: 2. In combination, a radar locator system, a pulse generator operable to duce pulse transmissions comprising one or more time spaced pulses occurring in any of a plurality of fixed time positions to form a plurality of different pulse code patterns which vary from pulse transmission to pulse transmission, a receiving means for receiving each of said pulse transmissions, a coder circuit in said receiving means responsive to the number and time position of said pulses to generate a reply signal having a characteristic dependent upon the pattern of said pulse transmissions, means for synchronizing the operation of said radar locator system and said pulse generator, and means for correlating the reply signals generated in said coder circuit and the echo pulses received by said radar locator system.