1. A COMPRESSOR SYSTEM FOR REFRIGERATION PLANTS COMPRISING AT LEAST TWO MULTI-CYLINDERED COMPRESSORS EACH HAVING AUTOMATIC FLUID-PRESSURE OPERABLE CAPACITY REGULATING EQUIPMENT IN SOME OF THE CYLINDERS THEREOF, A COMMON SUCTION CONDUIT, CONDUIT MEANS CONNECTING SAID SUCTION CONDUIT WITH EACH OF SAID COMPRESSORS, EACH OF SAID COMPRESSOR HAVING A DISTRIBUTION DEVICE, EACH OF SAID DISTRIBUTION DEVICES HAVING A PRESSURE-FLUID CHAMBER HAVING A PLURALITY OF OPENINGS ARRANGED FOR SEQUENTIAL OPENING AND CLOSING, A CONTROL VALVE IN EACH SAID CHAMBER MOVABLE THEREIN TO CONTROL SAID OPENING AND BEING RESPONSIVE IN ITS MOVEMENTS TO FLUID PRESSURE, EACH OF SAID COMPRESSORS HAVING A FLUID PUMP, EACH OF SAID PUMPS HAVING CONDUIT MEANS CONNECTED WITH THE DISCHARGE THEREOF AND WITH BOTH SAID COMMON SUCTION CONDUIT AND WITH THE PRESSURE FLUID CHAMBER OF THE CONTROL DEVICE CORRESPONDING TO THE RESPECTIVE COMPRESSORS, SAID CONNECTIONS WITH SAID PRESSURE FLUID CHAMBERS BEING ON ONE SIDE OF THE RESPECTIVE VALVES THEREOF, PRESSURE RESPONSIVE VALVE MEANS IN EACH OF THE CONDUIT MEANS BETWEEN SAID PUMP DISCHARGES AND SAID COMMON SUCTION CONDUIT, FLUID PRESSURE OPERABLE VALVE CONTROL MEANS OPERABLY CONNECTED WITH EACH OF SAID LAST-MENTIONED VALVE MEANS RESPECTIVELY, SAID VALVE CONTROL MEANS BEING CONNECTED WITH AND RESPONSIVE TO THE PRESSURE IN SAID COMMON SUCTION CONDUIT AND TENDING TO CLOSE THE RESPECTIVE VALVES WITH WHICH THEY ARE OPERABLY CONNECTED WHEN THE PRESSURE IN SAID SUCTION CONDUIT RISES, WHEREBY MORE OF THE DISCHARGE FROM THE RESPECTIVE PUMPS PASSES TO THE PRESSURE FLUID CHAMBER OF THE CORRESPONDING DISTRIBUTION DEVICE TO CAUSE SAID CORRESPONDING CONTROL VALVE TO MOVE, CONDUIT MEANS CONNECTING ONE OF SAID SEQUENTIAL OPENINGS OF EACH PRESSURE CHAMBER WITH ONE OF SAID CAPACITY REGULATING EQUIPMENTS, WHEREBY WHEN SAID SUCTION CONDUIT PRESSURE RISES SAID REGULATING VALVE OF A PREDETERMINED ONE OF SAID COMPRESSORS OPENS SAID CONDUIT MEANS CONNECTED WITH SAID ONE OF SAID CAPACITY REGULATING EQUIPMENTS TO INCREASE THE CAPACITY OF ITS CORRESPONDING COMPRESSOR, AND CONDUIT MEANS CONNECTING A SECOND SEQUENTIALLY ARRANGED OPENING IN THE PRESSURE CHAMBER OF THE DISTRIBUTION DEVICE OF SAID PREDETERMINED ONE OF SAID COMPRESSORS WITH THE FLUID PRESSURE CHAMBER OF ANOTHER COMPRESSOR OF THE SYSTEM ON ONE SIDE OF ITS CONTROL VALVE, WHEREBY A MAGNIFICATION OCCURS OF THE REGULATING EFFECT OF A PRESSURE VARIATION IMPULSE OCCURRING IN SAID COMMON SUCTION CONDUIT FOR CONTROLLING THE CAPACITY REGULATING EQUIPMENT OF THE COMPRESSORS OF SAID SYSTEM.