lt should also be recognized that this connection between needle 66 and stoppel 42 places both the secondary administration set 14 and the primary administration set 12 into fluid communication with connector 38 attached to connector 38 by any means well known in the art is a section of common tube 80 as is seen in fig2 common tube 80 is operatively associated with flow rate control valve 82 and as will be subsequently discussed flow rate control valve 82 is in turn operatively associated with the controller 10 for controlling the flow rate of fluid from either the primary administration set 12 or the secondary administration set 14 referring back to fig1 it is seen that a drop sensor 28 is operatively connected to the drip chamber 30 by engagement of the mounting flange 26 of drip chamber 30 into recesses not shown formed on the drop sensor 28 although there are many possible configurations for drop sensor 28 a drop sensor as disclosed in u s pat no 4 346 606 to cannon et al and assigned to the assignee of record of this application is suitable accordingly the disclosure and teachings of u s pat no 4 346 606 are incorporated herein by reference as can also be seen in fig1 the drop sensor 28 is electrically connected to the controller 10 by cable 84 secondary administration set 14.