A method and apparatus for parenteral administration of medical fluids has a normally closed clamp on the intraveneous feeding tube which is opened by means of an electromagnetic actuator at a preselected drop frequency rate and closed when a drop is detected by a conductive path established by the drop...http://www.google.es/patents/US4105028?utm_source=gb-gplus-sharePatente US4105028 - Positive control intravenous fluid administration
