A flow detector comprises at least two housing parts with a semiconductor chip having an integrated flow sensor arranged between the housing parts. The substrate with deposited layers is then heated to between 200-600\xb0 C. The pilot operated check valve also includes a valve member configured to move between an open position and a closed position to block air flow through the passageway. , when data which cannot be handled by the communication apparatus is contained, a global variable FORWARD is set to \u201c1\u201d.