A system for controlling the flow of fluid through a line (3). The system may include first and second valves (A, B; and 6, 7) in the line (3). Between the first and second valves is located a chamber (52, 82), part of which may be filled with fluid having a variable volume (52), and another part of...http://www.google.com.au/patents/US5349852?utm_source=gb-gplus-sharePatent US5349852 - Pump controller using acoustic spectral analysis
