Method and apparatus for distinct indication of sonar echoes reflected from different or multi-layer objects

Claim 1

SONAR APPARATUS FOR DISTINCTLY INDICATING ECHOES REFLECTED FROM DIFFERENT AND MULTI-LAYER OBJECTS, COMPRISING A SIGNAL INPUT STAGE FOR RECEIVING AN ECHO SIGNAL VOLTAGE HAVING A CARRIER FREQUENCY AND CONSTITUTING THE TOTALITY OF INDIVIDUAL ECHO PULSES, DEMODULATING DIODE MEANS CONNECTED TO SAID INPUT STAGE FOR DEMODULATING THE SIGNAL VOLTAGE, A FIRST NETWORK FOR FILTERING THE CARRIER FREQUENCY CONNECTED TO SAID DIODE MEANS, A SECOND NETWORK CONNECTED PARALLEL TO SAID FIRST NETWORK FOR DERIVING FROM THE DEMODULATED SIGNAL VOLTAGE A COMPENSATING VOLTAGE FROM THE LOWER ORDER FREQUENCY PARTS OF THE DEMODULATED SIGNAL VOLTAGE, AND ECHO INDIACTING MEANS, SAID FIRST AND SECOND NETWORKS HAVING RESPECTIVE OUTPUT TERMINALS CONNECTED IN VOLTAGE OPPOSED RELATION TO SAID INDICATING MEANS FOR CONTROLLING IT FOR EMPHASIZED INDICATION OF OTHERWISE INSUFFICIENTLY INDICATED TARGETS.