Gain control of limiter stage of a quadrature grid detector

Claim 1

IN A SYSTEM FOR DEMODULATING FREQUENCY MODULATED CARRIER WAVES, APPARATUS COMPRISING THE COMBINATION OF A LIMITER AMPLIFIER FOR FREQUENCY MODULATED CARRIER WAVES, SAID LIMITER AMPLIFIER INCLUDING AN ELECTRON DISCHARGE DEVICE HAVING A CATHODE, A CONTROL GRID, A SCREEN GRID AND AN ANODE, AN INPUT CIRCUIT COUPLED BETWEEN SAID CONTROL GRID AND CATHODE TO WHICH SAID FREQUENCY MODULATED CARRIER WAVES ARE APPLIED, AN OUTPUT CIRCUIT COUPLED BETWEEN SAID ANODE AND CATHODE, FREQUENCY MODULATION DETECTING MEANS COUPLED TO SAID OUTPUT CIRCUIT, SAID DETECTING MEANS INCLUDING A SECOND ELECTRON DISCHARGE DEVICE OPERATING AS A QUADRATURE GRID DETECTOR FOR DETECTING DIRECTLY MODULATED CARRIER WAVES OF RELATIVELY LARGE AMPLITUDE AND FOR DETECTING LOCKED OSCILLATIONS WHEN THE MODULATED CARRIER WAVES ARE OF RELATIVELY SMALL AMPLITUDE, MEANS FOR DERIVING FROM