Abstract: A fire alarm system comprises a central control station feeding through a plurality of parallel supply lines a direct current voltage to a corresponding plurality of remote alarm stations. Each station has a fire sensor including a reference ionization chamber and a measuring ionization chamber, both chambers being connected in series between the two supply lines and having a common intermediate electrode. A field effect transistor has a gate electrode connected to the intermediate electrode of the ionization chambers and a source drain conducting channel the conductivity of which is controlled by the gate electrode. The input resistance and the input capacitance of the field effect transistor is connected parallel to the reference ionization chamber and defines therewith a first relatively short time constant of about two seconds.

Abstract: A shock-, vibrations- and tampering-proof attachment means of an object, h as a signal producing insert of an ionization alarm system coaxially and non-rotatably to a support, such as for land-, marine- and air vehicles provides a spring assembly with a spring and biased coaxial protrusion in the bottom of the object with a helically wound canal running through the protrusion having end orifices in its surface. The support is provided with a U-shaped fork fixed with its yoke in it. A connecting means equipped with a rod traverses the protrusion perpendicularly to its axis. The rod is fastened to both free ends of the yoke. Optimum shapes and dimensions of the respective parts are established, also with the view of maintaining a minimum size of the object itself. The object with the fixed protrusion is mounted by rotation thereof to the support, thus hiding the attachment means and making them vibration proof and inaccessible from the outside.