relieved or vented by the influx of irrigation fluid along the pressure equalization or vent line 32 which directly communicates between the irrigation line 18 and the aspiration line 28 the vacuum is thereby quickly relieved by the head pressure of the bottle 12 via the vent solenoid or valve 34 this process is called 34 venting 34 the system the valve 34 is normally closed when the handpiece 20 is being used to aspirate fluid and tissue from a surgical site 16 when a blockage occurs in the aspiration line 28 such as when a tissue fragment occludes the axial bore in the ultrasonic tool of the handpiece 20 the increased suction in the aspiration line 28 is sensed by the pressure sensitive transducer apparatus 36 which in turn sends a signal to shut off the pump 26 the surgeon can then release the vacuum in the aspiration line 28 by momentarily opening the valve 34 to admit irrigation fluid from bottle 12 to the aspiration line 28 via the vent line 32 and through a special fitting 38 such as is shown and described in detail in u s pat no 4 832 685 as soon as the pressure has been equalized the transducer apparatus 36 detects the lower level of suction or vacuum and allows the surgeon to restart the pump 26 when the valve 34 is closed and the surgeon restarts the system the pump 26 will again.