SIGNAL TRAP DEVICE AND METHOD, RECORDING MEDIUM REPLAY DEVICE AND METHOD AND SIGNAL EXTRACTION DEVICE AND METHOD

摘要

A SIGNAL TRAP DEVICE AND METHOD FOR TRAPPING A DESIRED FM SIGNAL OUT OF A FREQUENCY MULTIPLEXED SIGNAL WHERE A PLURALITY OF FM SIGNALS ARE INCLUDED IN A FREQUENCY MULTIPLEXED FORM. A REPLAY SIGNAL REPRODUCED FROM A VIDEO CASSETTE TAPE IS SUPPLIED DIRECTLY TO A SUBTRACTER (21) WHILE BEING FED TO A FIXED DELAY CIRCUIT (22) AND A VARIABLE DELAYS CIRCUIT TO BE DELAYED THEREIN BY A PREDETERMINED DELAY TIME. THE DELAYED SIGNAL IS SUPPLIED ALSO TO THE SUBTRACTER (21), WHICH THEN SUBTRACTS THE DELAYED SIGNAL FROM THE REPRODUCED REPLAY SIGNAL AND OUTPUTS THE RESULT OF SUCH SUBTRACTION THEREFROM. THE DELAY TIME OF THE FIXED DELAY CIRCUIT IS SO SET AS TO CORRESPOND TO THE CENTER FREQUENCY OF THE CARRIER OF THE DESIRED FM SIGNAL TO BE TRAPPED. MEANWHILE THE DELAY TIME OF THE VARIABLE DELAY CIRCUIT IS SO SET AS TO CORRESPOND TO THE SIGNAL OBTAINED BY DEMODULATING THE DESIRED FM SIGNAL. THUS, THE DESIRED FM SIGNAL CAN BE TRAPPED PROPERLY WITHOUT ANY HARMFUL INFLUENCE ON THE OTHER FM SIGNAL.FIGURE 7