Means for the production of a voltage which depends upon the difference between two frequencies

Claim 1

IN A FREQUENCY CONTROL SYSTEM, A FIRST AND A SECOND GENERATOR OF OSCILLATIONS, THE FREQUENCY OF OSCILLTION OF SAID SECOND GENERATOR BEING CONTROLLED BY REGULATING VOLTAGE DEPENDING UPON THE DIFFERENCE BETWEEN THE FREQUENCIES OF OSCILLATION OF SAID GENERATORS, A COUNTER COUPLED TO EACH OF SAID GENERATOR BY MEANS OF A NORMALLY OPEN GATE CIRCUIT WHEREBY AFTER THE ARRIVAL OF A CONSTANT NUMBER OF CYCLES OF OSCILLATION EACH OF SAID COUNTER EMITS AN OUTPUT PULSE BRINGING THE COUNTER INTO ZERO POSITION FOR IMMEDIATE START OF THE NEXT COUNTING CYCLE, A PHASE DISCRIMINATOR COUPLED TO THE OUTPUT OF EACH COUNTER FOR PRODUCING A REGULATING VOLTAGE ACCORDING TO THE PHASE DIFFERENCE OF SAID OUTPUT PULSES, SAID REGULATING VOLTAGE BEING FUEL TO THE SECOND GENERATOR THROUGH A LOW-PASS FILTER, TWO COINCIDENCE CIRCUITS, THE OUTPUT OF EACH COINCIDENCE CIRCUIT BEING CONNECTED WITH THE CONTROL INPUT OF ONE OF SAID GATE CIRCUITS, ONE INPUT OF EACH COINCIDENCE CIRCUIT BEING CONNECTED CROSSWISE WITH THE OUTPUT OF ONE SAID COUNTERS AND THE OTHER INPUT OF EACH COINCIDENCE CIRCUIT BEING CONNECTED WITH MEANS FOR PRODUCING PULSES PRECEDING THE OUTPUT PULSES OF SAID COUNTERS IN TIME, WHEREBY AN OUTPUT PULSE OF ONE OF SAID COINCIDENCE CIRCUITS CLOSES ONE OF SAID GATE CIRCUITS.