Ionization type smoke detector

An ionization type smoke detector comprising:

• a smoke detecting section including an intermediate electrode and an outer electrode positioned opposite to each other to confine an outer ionization chamber therebetween into which smoke to be detected is introduced, and a reference resistance circuit electrically connected to said outer ionization chamber, said reference resistance circuit forming a reference resistance with respect to said outer ionization chamber;
• a sensor output circuit including:
• a first transistor having a gate and a source, said gate being connected to said intermediate electrode of said smoke detecting section, and a serial circuit connected to said source of and first transistor and consisting of a first fixed resistor and a first constant-current circuit having a first variable resistor for adjustment of an output current of said first constant-current circuit, said sensor output circuit producing a sensor output from a junction between said first constant-current circuit and said first fixed resistor of said serial circuit;
• a fire discriminating circuit for receiving said sensor output from said sensor output circuit and including a reference voltage generating circuit having a second variable resistor for reference voltage adjustment, said fire discrimination circuit producing a discrimination output when said sensor output from said sensor output means exceeds a reference voltage generated by said reference voltage generating circuit;
• and
• a fire signal transmitting circuit for receiving said discrimination output from said fire discriminating circuit and for transmitting a fire signal in response to said discrimination output from said fire discriminating circuit.