Frequency responsive network

Claim 1

A FREQUENCY SELECTIVE NETWORK COMPRISING: MEANS PROVIDING A SIGNAL INPUT TERMINAL AND A COMMON MEANS PROVIDING A SIGNAL INPUT TERMINAL AND A COMMON TERMINAL CONNECTED TO A POINT OF REFERENCE POTENTIAL FOR SAID NETWORK; INPUT CIRCUIT MEANS COUPLING A RESISTIVE CIRCUIT ELEMENT IN SERIES WITH A REACTIVE CIRCUIT ELEMENT ACROSS SAID SIGNAL INPUT AND COMMON TERMINALS; AMPLIFIER MEANS COUPLED TO ONE OF THE ELEMENTS OF SAID INPUT CIRCUIT MEANS; FIRST SIGNAL COMBINING MEANS HAVING A FIRST INPUT CIRCUIT COUPLED TO SAID AMPLIFIER MEANS, A SECOND INPUT CIRCUIT COUPLED TO SAID SIGNAL INPUT TERMINAL, AND AND OUTPUT TERMINAL, SAID FIRST SIGNAL COMBINING MEANS PROVIDING IMPEDANCE ISOLATION BETWEEN SAID OUTPUT TAERMINAL AND SAID FIRST AND SECOND IMPUT TERMINALS; THE AMPLIFICATION PROVIDED BY SAID AMPLIFIER MEANS AND THE RELATIVE PHASES OF THE SIGNALS APPLIED TO THE FIRST AND SECOND INPUT CIRCUITS OF THE FIRST COMBINING MEANS BEING SUCH AS TO PROVIDE AN OUTPUT SIGNAL AT THE OUTPUT TERMINAL OF SAID FIRST SIGNAL COMBINING MEANS WHICH IS PROPORTIONAL TO THE DIFFERENCE BETWEEN THE VOLTAGE APPLIED BETWEEN SAID INPUT AND COMMON TERMINALS AND TWO TIMES THE VOLTAGE DEVELOPED ACROSS SAID ONE OF THE ELEMENT OF SAID SIGNAL INPUT CIRCUIT MEANS; SUMMING CIRCUIT MEANS INCLUDING A FIRST INPUT AND A REACTIVE ELEMENT CONNECTED IN SERIES BETWEEN SAID OUTPUT TERMINAL AND SAID POINT OF REFERENCE POTENTIAL FOR SAID NETWORK, THE TIME CONSTANT OF SAID SUMMING CIRCUIT BEING SUBSTANTIALLY EQUAL TO THE TIME CONSTANT OF SAID INPUT CIRCUIT MEANS; SECOND SIGNAL COMBINING MEANS INCLUDING A FIRST INPUT CIRCUIT COUPLED TO THE JUNCTION OF THE RESISTIVE AND REACTIVE CIRCUIT ELEMENTS OF SAID SUMMING CIRCUIT MEANS, A SECOND INPUT CIRCUIT COUPLED TO SAID ONE OF THE ELEMENTS OF SAID SIGNAL INPUT CIRCUIT MEANS, AND AN OUTPUT TERMINAL, THE RELATIVE AMPLITUDES AND PHASES OF THE SIGNALS APPLIED TO THE FIRST AND SECOND INPUT CIRCUITS BEING SUCH AS TO PRODUCE AN OUTPUT SIGNAL PORPORTIONAL TO THE SUM OF THE VOLTAGES APPEARING AT THE JUCTION OF THE ELEMENTS OF SAID SUMMING CIRCUIT AND ACROSS SAID ONE OF THE ELEMENTS OF SAID INPUT CIRCUIT AND RESPECTIVELY SAID SECOND SIGNAL PROVIDING IMPEDANCE ISOLATION BETWEEN SAID FIRST SIGNAL INPUT CIRCUIT AND RESPECTIVELY SAID SECOND SIGNAL INPUT CIRCUIT AND SAID OUTPUT TERMINAL; OUTPUT CIRCUIT MEANS COUPLED BETWEEN THE OUTPUT TERMINAL OF SAID SECOND SIGNAL COMBINING MEANS AND SAID POINT OF REFERENCE POTENTIAL; AND MEANS FOR ADJUSTING ONE OF THE ELEMENTS OF SAID SUMMING CIRCUIT MEANS TO TUNE SAID NETWORK.