Gain control circuit with selectable attack time constant that is independent of a fixed decay time constant

Claim 1

A GAIN CONTROL CIRCUIT OF THE TYPE USED TO AUTOMATICALLY CONTROL THE GAIN OF AMPLIFYING MEANS, SAID CIRCUIT COMPRISING: MEANS ADAPTED TO RECEIVE AN OUTPUT FROM SAID AMPLIFYING MEANS TO BE CONTROLLED; AMPLITUDE DETECTOR MEANS FOR CONVERTING SAID OUTPUT TO A D.C. VOLTAGE; A FIRST CAPACITOR THAT IS CHARGED IN RESPONSE TO AN INCREASE IN SAID D.C. VOLTAGE FROM SAID DETECTOR MEANS; RESISTANCE MEANS THROUGH WHICH SAID FIRST CAPACITOR DISCHARGES WHEN SAID D.C. VOLTAGE IS DECREASED; A SECOND CAPACITOR; A SELECTIVELY BIASED DIODE CONNECTED TO SAID SECOND CAPACITOR, SWITCH MEANS FOR CONTROLLING THE BIAS ON SAID DIODE SO THAT SAID SECOND CAPACITOR IS CONNECTED IN PARALLEL WITH SAID FIRST CAPACITOR AND CHARGED THERWITH ONLY WHEN SAID DIODE IS FORWARD-BIASED; ONE SWITCH POSITION PROVIDING A FIRST CHARGE TIME AND THE OTHER SWITCH POSITION PROVIDING A SECOND CHARGE TIME; AND DISCHARGE MEANS CONNECTED TO SAID SECOND CAPACITOR FOR DISCHARGING SAID SECOND CAPACITOR THERETHROUGH WHENEVER SAID FIRST CAPACITOR STARTS TO DISCHARGE WHEREBY THE DISCHARGE TIME CONSTANT TO SAID GAIN CONTROL CIRCUIT IS CONSTANT.