improvements in infusion controlling apparatus used in limiting the flow rate of an intravenous solution to a patient . the improvements provide coarse and fine orientations of a casette through which the solution passes relative to a controller which valves the casette &# 39 ; s inlet and outlet to provide measured volumes of fluid . the coarse alignment device includes spaced apart metal sections which grasp onto the casette and move it towards the controller &# 39 ; s valving members . as the casette reaches the valving members , protuberances on the controller fit into indentations on the casette , as the fine adjustment . the indentations into which the protuberances fit form part of the casette &# 39 ; s base section of plastic notwithstanding the location of a cover slip between these two items . the valving members couple to a rocker arm which pivots about a point located at its middle and has magnetic poles at its ends . the rocker arm &# 39 ; s pivot point over the center leg of an e - frame electromagnet allows the arm to rotate between two orientations in which one of its magnetic poles contacts a side leg of the e - frame electromagnet . current passing through a coil located on the center leg of the electromagnet moves the rocker arm between these positions , depending upon the current &# 39 ; s direction . with no current in the coil , the arm &# 39 ; s magnets and the e - frame provide a bistable magnetic device in which the rocker arm forces one of the valving members to close either the casette &# 39 ; s inlet or its outlet . this prevents the uncontrolled passage of fluid through the casette to the patient .