Overload protection circuit for high impedance amplifiers

Claim 1

AN OVERLOAD PROTECTION AND LIMITER CIRCUIT FOR AN ELECTRICAL SIGNAL AMPLIFIER HAVING A HIGH INPUT IMPEDANCE, SAID AMPLIFIER INCLUDING A PAIR OF INPUT TERMINALS, A PAIR OF OUTPUT TERMINALS, A FIRST OF SAID INPUT AND A FIRST OF SAID OUTPUT TERMINALS BEING CONNECTED IN COMMON, AND A LEAD CONNECTED TO SAID AMPLIFIER PROVIDING A SIGNAL INDICATING THE CONDITION OF LOADING OF SAID AMPLIFIER, SAID LEAD BEING CONNECTED TO A POINT IN SAID AMPLIFIER OTHER THAN THE SECOND OUTPUT TERMINAL THEREOF, SAID POINT BEING ISOLATED FROM SAID SECOND OUTPUT TERMINAL, SID CIRCUIT COMPRISING, IN COMBINATION, A CURRENT SOURCE, A SWITCH INCLUDING MEANS RESPONSIVE TO THE SIGNAL ON SAID LEAD FOR OPERATING SAID SWITCH, FIRST MEANS CONNECTING SAID CURRENT SOURCE BETWEEN THE FIRST OUTPUT TERMINAL OF SAID AMPLIFIER AND A FIRST TERMINAL OF SAID SWITCH, SECOND MEANS CONNECTING SAID FIRST TERMINAL OF SAID SWITCH TO SAID OVERLOAD SIGNAL LEAD, THIRD MEANS CONNECTING A SECOND TERMINAL OF SAID SWITCH TO THE SECOND OF SAID AMPLIFIER INPUT TERMINALS, AND FOURTH MEANS CONNECTING AN IMPEDANCE IN SERIES BETWEEN THE SECOND OF SAID INPUT TERMINALS AND A TERMINAL TO WHICH THE SIGNAL SAID AMPLIFIER IS TO AMPLIFY IS APPLIED.