There is provided: first to fourth magnetic pole yokes 13-16 magnetized by the magnets 11, 12 having both poles on these opposite faces to establish a magnetic pole; and a vibrating membrane 17 disposed between the magnets 11, 12 and electromagnetically coupled to the yokes 13-16 by energizing a meandering coil pattern 17b thereon to vibrate in a predetermined direction. The accessory housing receives a system sensing device such as an absolute pressure sensor or a differential pressure sensor in fluid tight relation to the housing. The pressured steam is used to drive a steam-powered engine that drives an electrical generator whose electricity powers the system. Each S data set is identified by its unique identification information.