Frequency discriminator

Claim 1

A FREE RUNNING MULTIVIBRATOR COMPRISING: A PAIR OF AMPLIFYING DEVICES EACH HAVING AN INPUT AND AN OUTPUT WITH THE OUTPUT OF EACH CONNECTED BY A CAPACITOR TO THE INPUT OF THE OTHER, AND RESISTIVE BIASING CIRCUITS CONNECTED TO SAID INPUTS, SUCH THAT SAID MULTIVIBRATOR NORMALLY OSCILLATES AT A MEDIAN FREQUENCY DETERMINED BY THE TIME CONSTANT OF SAID CAPACITORS AND RESISTANCE OF SAID BIASING CICUITS TO PRODUCE AN ALTERNATING OUTPUT POTENTIAL HAVING POSITIVE AND NEGATIVE HALF CYCLES OF EQUAL DIRECTION; MEANS FOR APPLYING TO THE INPUTS OF BOTH AMPLIFYING DEVICES AN A.C. SIGNAL TO BE FREQUENCY COMPARED WITH SAID MEDIAN FREQUENCY SUCH THAT FREQUENCY DIFFERENCES BETWEEN SAID MEDIAN FREQUENCY AND SAID A.C. SIGNAL ARE REFLECTED IN SAID OUTPUT POTENTIAL AS POSITIVE AND NEGATIVE HALF CYCLES OF UNEQUAL DURATION; MEANS CONNECTED TO SAID MULTIVIBRATOR FOR FILTERING SAID OUTPUT POTENTIAL TO PRODUCE A UNIDIRECTIONAL POTENTIAL OF POLARITY AND MAGNITUDE CORRESPONDING TO THE DIFFERENCE BETWEEN THE DURATIONS OF SAID POSITIVE AND NEGATIVE HALF CYCLES; MEANS FOR APPLYING SAID UNIDIRECTIONAL POTENTIAL TO THE INPUTS OF BOTH SAID AMPLIFYING DEVICES; AND MEANS FOR INDICATING THE POLARITY AND MAGNITUDE OF SAID UNIDIRECTIONAL POTENTIAL.