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Combustion product detector

Image Number 2 for United States Patent #4081684.

A combustion product detector contains a single ionization chamber having a radioactive source therein. It is provided with means to test the function of the device. The means includes an electrically non-conductive member which may be introduced in the ionization chamber to simulate (in effect) the presence of smoke in the chamber. Housing for the chamber is constructed and mounted to shield the components contained therein. An FET and resistors are closely coupled to a radioactive source holder and to a printed circuit board on which the housing is mounted. A metal coil spring electrically connects the non-conductive test member and the housing to discharge static. The test member may be removed readily to permit inspection and cleaning of the radioactive source surface. The device may be powered from a battery or from AC line current with or without a standby battery to automatically power the device in the event of line current failure and may be provided with a circuit to produce a signal in the event of power failure.

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