Varying repetition rate pulse echo system

Claim 1

IN PULSE ECHO APPARATUS INCLUDING A RADIO-FREQUENCY PULSE TRANSMITTER, A RECEIVER AND AN INDICATOR DISPLAYING THE POSITION OF ECHOS ON A TRACE, MEANS FOR SELECTING DISPLAY ECHOS FROM MOVING TARGETS WHILE SUPPRESSING ECHOS FROM FIXED TARGETS, COMPRISING PULSE TRAIN GENERATING MEANS FOR PRODUCING AT LEAST TWO TRAINS OF PULSES, THE PULSES IN EACH TRAIN BEING DIFFERENTLY SPACED IN TIME AND CONTROLLING THE TRANSMISSION OF RADIO FREQUENCY PULSES; A PHASE COMPARER CONNECTED TO THE INDICATOR AND TO THE RECEIVER BY A FIRST PATH; TWO DIFFERENT DELAY LINES CONNECTED BETWEEN SAID RECEIVER AND SAID COMPARER BY A SECOND PATH; SWITCHING MEANS CONNECTED BETWEEN SAID DELAY LINES AND SAID COMPARER AND SELECTING THE DELAY LINE PASSING THE ECHO PULSES, SAID SWITCHING MEANS BEING CONNECTED TO SAID PULSE TRAIN GENERATING MEANS TO SELECT THE DEGREE OF DELAY OF THE ECHO PULSES BY SWITCHING THE DELAY LINES SO THAT IN EACH ALTERNATE CONDITION THE DELAY IS EQUAL IN TIME TO THE INTERVAL BETWEEN RADIATED PULSES, THE COM PARER COMPARING THE PHASE OF THE PULSES ARRIVING VIA THE FIRST AND SECOND PATHS AND INITIATING AN INDICATION ON SAID TRACE WHERE THE PHASES ARE DIFFERENT.