cap 202 as in fig2 a and fig2 b when the pump 200 enters the overload state as shown in fig2 c then the switch opens and feedback is fed to the drive circuit if the feedback is not received during the maximum pulse period used for pump 100 then an error has occurred and pump 200 operation can be discontinued the piston_nc 211 feedback is shown as connected directly to the top cap 202 which indicates that the top cap 202 is either made of a conductive material e g metal or is coated with an appropriately conductive material if the design of a given pump requires the top cap 202 to be made of an insulating material then the piston_nc 211 feedback can be moved to the inner surface of the top cap 202 so that the piston_nc 211 feedback is in direct contact with the overload piston 206 in the inactive state as shown in fig2 a an advantage of pump 200 is fault detection based on the feedback from normally closed switch 211 if the switch is not activated in the maximum pulse duration the pump also saves energy because it terminates the activation pulse when full pump action is achieved minimizing energy consumption is extremely important for a portable insulin pump as it maximizes the time the pump can be used without inconveniencing the user fig2 c shows the pump in the.