Fire detector

Claim 2

In a detecting device including: a power source; sensor means for providing a sensor signal representative of a predetermined sensed condition, said sensor means being connected in circuit with said power source; alarm means for providing an alarm when the predetermined condition is sensed, said alarm being connected in circuit with said power source; the improvement comprising; adjustable means for providing an adjustable reference signal for varying the sensitivity of said device, said adjustable means being connected in circuit with said power source; indicator means for indicating the condition of said power source, said indicator means being connected in circuit with said power source; first comparison means for comparing the amplitudes of the reference signal and the sensor signal, said first comparison means being connected to said power source, said sensor means, said adjustable means and said alarm means, said first comparision means providing a first signal for operating said alarm means when the sensor signal has a first predetermined relationship to the reference signal, said first comparison means providing a second signal when said sensor signal has a second predetermined relationship to the referece signal; signal offsetting means connected to said first comparison means for increasing the amplitude of said second signal to a third signal; and second comparison means for comparing the amplitudes of the third signal and the sensor signal, said second comparison means being connected to said signal offsetting means, the interconnection of said first comparison means and said sensing means, and said indicator means, said second comparison means operating said indicator means to indicate improper adjustment of said adjustable means, said first comparison means being incapable of operating said alarm means when the third signal has a predetermined relationship to the sensor signal; whereby said indicator means indicates improper operation of said device should said power source fail, or should said adjustable means be improperly set.

Claim 3

In a detecting device as in claim 1, wherein said indicator means is energizable by said power source to indicate proper and de-energizable to indicate improper operation thereof, and said second comparison means de-enerigizes said indicator means to indicate proper adjustment of said adjustable means.

Claim 4

In a detecting device as in claim 1, wherein said first comparison means includes a common impedance, a pair of transistors each having base, emitter and collector electrodes, said emitter electrodes being coupled together and to said common impedance, the base of one transistor being coupled to said adjustable means, the base of the second transistor being coupled to said sensor means, the collector of said second transistor being coupled to said alarm means, said second comparision means includes a third transistor coupled to said common impedance and said sensor means, and said signal offsetting means comprises a diode connected between said second and third transistors.

Claim 5

In a detecting device as in claim 1, wherein said first comparison means includes a differential amplifier having first and second inputs, said first input being connected to said adjustable means and said second input being connected to said sensor means, said adjustable means including a potentiometer.

Claim 6

In a detecting device as in claim 1, wherein said signal offsetting means is a diode.

Claim 7

In a detecting device as in claim 1, wherein said alarm means includes a first switch device and an alarm device in series, and wherein said indicator means includes a second switch device and an indicator device in series, said first switch device being operated by said first comparison means and said second switch device being operated by said second comparison means.

Claim 8

In a detecting device as in claim 6, wherein said first and second switch devices are SCRs, said first comparison means comprises a pair of transistors having their emitters connected together and the collector of one of said transistors connected to the gate of the SCR comprising said first switch device, and said second comparison means comprises a third transistor having its emitter connected to said signal offsetting means, its base connected to the base of said one transistor and its collector connected to the gate of the SCR comprising said second switch device.

Claim 9

In a detecting device as in claim 6, wherein said first and second switch devices are transistors, said first comparison means comprises a pair of transistors having their emitters connected together and the collector of one of said pair of transistors connected to the base of the transistor comprising said first switch device, and said second comparison means comprises another transistor having its emitter connected to the signal offsetting means, its base connected to the base of said one transistor and its collector connected to the base of the transistor comprising said second switch device.

Claim 10

A detecting device comprising: a source of power; sensor means for providing a signal voltage representative of a predetermined sensed condition and being connected to said power source; a source of reference potential connected in circuit with said power source; first voltage comparison means connected to said power source, said sensor means and said source of reference potential, said first voltage comparison means being responsive to a first predetermined difference in the amplitudes of said reference potential and said signal voltage; alarm means connected to said first voltage comparison means and responsive thereto for providing an alarm in response to said first predetermined difference in the amplitudes of said reference potential and said signal voltage; second voltage comparison means coupled to said source of reference potential and said sensing means, said second voltage comparison means being responsive to a second predetermined difference in the amplitudes of said reference potential and said signal voltage; and indicator means connected to said power source and said second voltage comparison means, said indicator means being responsive to said second voltage comparison means for providing an indication in response to said second predetermined difference in the amplitudes of said reference potential and said signal voltage; said first voltage comparison means including a common impedance, a pair of transistors each having base, emitter and collector electrodes, said emitter electrodes being coupled together and to said common impedance, the base of one of said transistors being coupled to said source of reference potential, the base of the other of said transistors being coupled to said sensor means, and one of said collectors being coupled to said alarm means; said second comparison means including transistor means having first, second and third electrodes and voltage offsetting means including a diode connected in circuit with said emitters and said common impedance, said first electrode being coupled to said diode, said second electrode being coupled to the interconnection of said first voltage comparison means and said sensor means, said third electrode being coupled to said indicator means.

Claim 11

A detecting device comprising: a source of power; sensor means for providing a signal voltage representative of a predetermined sensed condition and being connected to said power source; a source of reference potential connected in circuit with said power source; first voltage comparison means connected to said power source, said sensor means and said source of reference potential, said first voltage comparison means being responsive to a first predetermined difference in the amplitudes of said reference potential and said signal voltage; alarm means connected to said first voltage comparison means and responsive thereto for providing an alarm in response to said first predetermined difference in the amplitudes of said reference potential and said signal voltage; second voltage comparison means coupled to said source of reference potential and said sensing means, said second voltage comparison means being responsive to a second predetermined difference in the amplitudes of said reference potential and said signal voltage; and indicator means connected to said power source and said second voltage comparison means, said indicator means being responsive to said second voltage comparison means for providing an indication in response to said second predetermined difference in the amplitudes of said reference potential and said signal voltage; said first voltage comparison means including a common impedance, a pair of transistors each having base, emitter and collector electrodes, said emitter electrodes being coupled together and to said common impedance, the base of one of said transistors being coupled to said source of reference potential, the base of the other of said transistors being coupled to said sensor means, and one of said collectors being coupled to said alarm means; said second comparison means including transistor means having first, second and third electrodes and voltage offsetting means including a diode connected in circuit with said emitters and said common impedance, said first electrode being coupled to said diode, said second electrode being coupled to the interconnection of said first voltage comparison means and said sensor means, said third electrode being coupled to said indicator means.

Claim 12

A detecting device comprising: a power source; sensor means for providing a sensor signal representative of a predetermined sensed condition, said sensor means being connected in circuit with said power source; alarm means for providing an alarm when the predetermined condition is sensed, said alarm being connected in circuit with said power source; adjustable means for providing an adjustable reference signal for varying the sensitivity of said device, said adjustable means being connected in circuit with said power source; indicator means for indicating the condition of said power source and of said sensor means, said indicator means being connected in circuit with said power source; first comparison means for comparing the reference signal and the sensor signal, said first comparison means being connected to said power source, said sensor means, said adjustable means and said alarm means, said first comparison means providing a first signal for operating said alarm means when the sensor signal has a predetermined relationship to the reference signal, said first comparison means providing a second signal when said sensor signal has a second predetermined relationship to the reference signal, and second comparison means for comparing the second signal from said first comparison means to the sensor signal, said second comparison means being connected to said first comparison means, said sensing means and said indicator means, said second comparison means operating said indicator means to indicate improper adjustment of said adjustable means, said first comparison means being incapable of operating said alarm means when the second signal from said first comparison means has a predetermined relationship to the sensor signal; whereby said indicator means indicated improper operation of said device should said power source or sensor means fail, or should said adjustable means be improperly set.

Claim 13

A detecting device comprising: a power source; sensor means for providing a sensor signal representative of a predetermined sensed condition, said sensor means being connected in circuit with said power source; alarm means for providing an alarm when the predetermined condition is sensed, said alarm being connected in circuit with said power source; adjustable means for providing an adjustable reference signal for varying the sensitivity of said device, said adjustable means being connected in circuit with said power source; indicator means for indicating the condition of said power source and of said sensor means, said indicator means being connected in circuit with said power source; first comparison means for comparing the reference signal and the sensor signal, said first comparison means being connected to said power source, said sensor means, said adjustable means and said alarm means, said first comparison means providing a first signal for operating said alarm means when the sensor signal has a predetermined relationship to the reference signal, said first comparison means providing a second signal when said sensor signal has a second predetermined relationship to the reference signal, and second comparison means for comparing the second signal from said first comparison means to the sensor signal, said second comparison means being connected to said first comparison means, said sensing means and said indicator means, said second comparison means operating said indicator means to indicate improper adjustment of said adjustable means, said first comparison means being incapable of operating said alarm means when the second signal from said first comparison means has a predetermined relationship to the sensor signal; whereby said indicator means indicated improper operation of said device should said power source or sensor means fail, or should said adjustable means be improperly set.

Claim 14

A detecting device as in claim 10, wherein said indicator means in energizable by said power source to indicated proper and de-energizable to indicate improper operation thereof, and said second comparison means de-energizes said indicator means to indicate improper adjustment of said adjustable means and includes signal offsetting connected to said first comparison means.

Claim 15

A detecting device as recited in claim 10, wherein said first comparison means includes a common impedance, a pair of transistors each having base, emitter and collector electodes, said emitter electrodes being coupled together and to said common impedance, the base of one transistor being coupled to said adjustable means, the base of the second transistor being coupled to said sensor means, the collector of said second transistor being coupled to said alarm means; said second comparison means includes a third transistor connected to the junction of said emitters and said common impedance and to said sensor means, and signal offsetting means being connected between said junction and said second transistor.

Claim 16

A detecting device as recited in claim 12, wherein said signal offsetting means is a diode.

Claim 17

A detecting device as in claim 10, wherein said sensor means includes an ionization device whose impedance changes upon the presence of products of combustion, and an amplifying device connected to said ionization device and said first and second comparison means.

Claim 18

A detecting device as in claim 14, wherein said amplifying device is a MOS-FET having a gate, drain and source, said gate being connected to said ionization device, said source being connected to said first and second comparison means and said drain being connected to said power source.

Claim 19

A fire detector adapted to be connected to a pair of AC power lines comprising a transformer for reducing the voltage of said AC power lines, said transformer having a pair of low voltage output lines, rectifying means connected to said low voltage lines for rectifying low voltage AC power to DC power, said rectifying means having a pair of DC output voltage power lines, filtering means connected between said pair of DC voltage lines, voltage regulating means connected to said pair of DC voltage lines, an ionization device having a target and chamber, first impedance means connected in series with said ionization device, the circuit of said ionization device and said first impedance means being in parallel with said voltage regulating means, sensor means, second and third impedance means connected in series with said sensor means, the circuit of said second and third impedance means and said sensor means being in parallel with said voltage regulating means and connected to said ionization device, fourth impedance means connected to one of said DC lines, first transistor means, second transistor means, said first and second impedance means having common emitters connected to said forth impedance means, the collector of one of said transistor means being connected to the other of said DC lines, the base of said other transistor means being connected to the junction of said sensor means and said second impedance means, fifth impedance means connected between said DC lines, the base of said one transistor means being adjustably connected to said fifth impedance means for providing variable sensitivity of the detector to products of combustion, alarm means, first switch means in series with said alarm means, said alarm means and first switch means being connected to said DC lines, the collector of the other of said transistor means being connected to said first switch means, third transistor means, the emitter of said third transistor means being connected to said fourth impedance means, the base of said third transistor means being connected to the base of said other transistor means, indicator means, second switch means in series with said indicator means, said indicator means and said second switch means being connected to said DC lines, the collector of said third transistor means being connected to said second switch means, whereby should products of combustion be present an alarm is given by said alarm means and should the sensitivity of the detector be too high as established by the adjustment of the connection of the base of said one transistor means to said fifth impedance means an alarm is given by said alarm means or should the sensitivity of the detector be too low as established by said adjustment or should said sensor means or power lines fail an indication is given by said indicator means and said alarm is not given.

Claim 20

A fire detector adapted to be connected to a pair of AC power lines comprising a transformer for reducing the voltage of said AC power lines, said transformer having a pair of low voltage output lines, rectifying means connected to said low voltage lines for rectifying low voltage AC power to DC power, said rectifying means having a pair of DC output voltage power lines, filtering means connected between said pair of DC voltage lines, voltage regulating means connected to said pair of DC voltage lines, an ionization device having a target and chamber, first impedance means connected in series with said ionization device, the circuit of said ionization device and said first impedance means being in parallel with said voltage regulating means, sensor means, second and third impedance means connected in series with said sensor means, the circuit of said second and third impedance means and said sensor means being in parallel with said voltage regulating means and connected to said ionization device, fourth impedance means connected to one of said DC lines, first transistor means, second transistor means, said first and second impedance means having common emitters connected to said forth impedance means, the collector of one of said transistor means being connected to the other of said DC lines, the base of said other transistor means being connected to the junction of said sensor means and said second impedance means, fifth impedance means connected between said DC lines, the base of said one transistor means being adjustably connected to said fifth impedance means for providing variable sensitivity of the detector to products of combustion, alarm means, first switch means in series with said alarm means, said alarm means and first switch means being connected to said DC lines, the collector of the other of said transistor means being connected to said first switch means, third transistor means, the emitter of said third transistor means being connected to said fourth impedance means, the base of said third transistor means being connected to the base of said other transistor means, indicator means, second switch means in series with said indicator means, said indicator means and said second switch means being connected to said DC lines, the collector of said third transistor means being connected to said second switch means, whereby should products of combustion be present an alarm is given by said alarm means and should the sensitivity of the detector be too high as established by the adjustment of the connection of the base of said one transistor means to said fifth impedance means an alarm is given by said alarm means or should the sensitivity of the detector be too low as established by said adjustment or should said sensor means or power lines fail an indication is given by said indicator means and said alarm is not given.

Claim 21

A fire detector as in claim 16, wherein said sensor means is a MOS-FET having its gate connected to said ionization device and a source connected to said other and third transistor means, said first and second switch means comprise darlington amplifier pairs, and said fourth impedance means comprises a resistor in series with a diode, said emitter of said third transistor means being connected to the junction of said resistor and diode.

Claim 22

A fire detector adapted to be connected to a pair of AC power lines comprising rectifying means connected to said AC power lines for rectifying the AC power to DC power, said rectifying means having a pair of DC output voltage power lines, voltage regulating means connected to said pair of DC voltage lines, an ionization device having a target and chamber, first impedance means connected in series with said ionization device, the circuit of said ionization device and said first impedance means being in parallel with said voltage regulating means, sensor means, second and third impedance means connected in series with said sensor means, the circuit of said second and third impedance means and said sensor means being in parallel with said voltage regulating means and connected to said ionization device, fourth impedance means connected to one of said DC lines, first transistor means, second transistor means, said first and second transistor means having common emitters connected to said forth impedance means, the collector of one of said transistor means being connected to the other of said DC lines, the base of said other transistor means being connected to the junction of said sensor means and said second impedance means, fifth impedance means connected between said DC lines, the base of said one transistor means being adjustably connected to said fifth impedance means for providing variable sensitivity of the detector to products of combustion, alarm means, first switch means in series with said alarm means, said alarm means and first switch means being connected to said AC lines, the collector of the other of said transistor means being connected to said first switch means, third transistor means, the emitter of said third transistor means being connected to said fourth impedance means, the base of said third transistor means being connected to the base of said other transistor means, indicator means, second switch means in series with said indicator means, said indicator means and said second switch means being connected to said AC lines, the collector of said third transistor means being connected to said second switch means, whereby should products of combustion be present in an alarm is given by said alarm means and should the sensitivity of the detector be too high as established by the adjustment of the connection of the base of said one transistor means to said fifth impedance means an alarm is given by said alarm means or should the sensitivity of the detector be too low as established by said adjustment or should said sensor means or power lines fail an indication is given by said indicator means and said alarm is not given.

Claim 23

A fire detector adapted to be connected to a pair of AC power lines comprising rectifying means connected to said AC power lines for rectifying the AC power to DC power, said rectifying means having a pair of DC output voltage power lines, voltage regulating means connected to said pair of DC voltage lines, an ionization device having a target and chamber, first impedance means connected in series with said ionization device, the circuit of said ionization device and said first impedance means being in parallel with said voltage regulating means, sensor means, second and third impedance means connected in series with said sensor means, the circuit of said second and third impedance means and said sensor means being in parallel with said voltage regulating means and connected to said ionization device, fourth impedance means connected to one of said DC lines, first transistor means, second transistor means, said first and second transistor means having common emitters connected to said forth impedance means, the collector of one of said transistor means being connected to the other of said DC lines, the base of said other transistor means being connected to the junction of said sensor means and said second impedance means, fifth impedance means connected between said DC lines, the base of said one transistor means being adjustably connected to said fifth impedance means for providing variable sensitivity of the detector to products of combustion, alarm means, first switch means in series with said alarm means, said alarm means and first switch means being connected to said AC lines, the collector of the other of said transistor means being connected to said first switch means, third transistor means, the emitter of said third transistor means being connected to said fourth impedance means, the base of said third transistor means being connected to the base of said other transistor means, indicator means, second switch means in series with said indicator means, said indicator means and said second switch means being connected to said AC lines, the collector of said third transistor means being connected to said second switch means, whereby should products of combustion be present in an alarm is given by said alarm means and should the sensitivity of the detector be too high as established by the adjustment of the connection of the base of said one transistor means to said fifth impedance means an alarm is given by said alarm means or should the sensitivity of the detector be too low as established by said adjustment or should said sensor means or power lines fail an indication is given by said indicator means and said alarm is not given.

Claim 24

A fire detector as in claim 18, wherein said sensor means is a MOS-FET having its gate connected to said ionization device and a source connected to said other and third transistor means, said first and second switch means comprise SCRs, and said fourth impedance means comprises a resistor in series with a diode, said emitter of said third transistor means being connected to the junction of said resistor and diode.

Claim 25

A fire detector adapted to be connected to a pair of AC power lines, comprising a transformer for reducing the voltage of said AC power lines, said transformer having a pair of low voltage output lines, rectifying means connected to said low voltage lines for rectifying the low voltage AC power to DC power, said rectifying means having a pair of DC output voltage lines, filtering means connected between said pair of DC voltage lines, voltage regulating means connected to said pair of DC voltage lines, an ionization device having a target and chamber, first impedance means connected in series with said ionization device, the circuit of said ionization device and said first impedance means being in parallel with said voltage regulating means, sensor means, second and third impedance means connected in series with said sensor means, the circuit of said second and third impedance means and said sensor means being in parallel with said voltage regulating means and connected to said ionization device, fourth impedance means connected to one of said DC lines, first transistor means, second transistor means, said first second transistor means having common emitters connected to said fourth impedance means, the collector of one of said transistor means being connected to the other of said DC lines, the base of said other transistor means being connected to the junction of said sensor means and said second impedance means, fifth impedance means connected between said DC lines, the base of said one transistor means being adjustably connected to said first impedance means for providing variable sensitivity of the detector to products of combustion, alarm means, switch means in series with said alarm means, said alarm means and switch means being connected to said DC lines, the collector of the other of said transistor means being connected to said switch means, indicator means connected to said DC lines, whereby should products of combustion be present an alarm is given by said alarm means and should the sensitivity of the detector be too high as established by the adjustment of the connection of the base of said one transistor means to said fifth impedance means an alarm is given by said alarm means or should said power lines fail an indication is given by said indicator means and said alarm is not given.

Claim 26

A fire detector adapted to be connected to a pair of AC power lines, comprising a transformer for reducing the voltage of said AC power lines, said transformer having a pair of low voltage output lines, rectifying means connected to said low voltage lines for rectifying the low voltage AC power to DC power, said rectifying means having a pair of DC output voltage lines, filtering means connected between said pair of DC voltage lines, voltage regulating means connected to said pair of DC voltage lines, an ionization device having a target and chamber, first impedance means connected in series with said ionization device, the circuit of said ionization device and said first impedance means being in parallel with said voltage regulating means, sensor means, second and third impedance means connected in series with said sensor means, the circuit of said second and third impedance means and said sensor means being in parallel with said voltage regulating means and connected to said ionization device, fourth impedance means connected to one of said DC lines, first transistor means, second transistor means, said first second transistor means having common emitters connected to said fourth impedance means, the collector of one of said transistor means being connected to the other of said DC lines, the base of said other transistor means being connected to the junction of said sensor means and said second impedance means, fifth impedance means connected between said DC lines, the base of said one transistor means being adjustably connected to said first impedance means for providing variable sensitivity of the detector to products of combustion, alarm means, switch means in series with said alarm means, said alarm means and switch means being connected to said DC lines, the collector of the other of said transistor means being connected to said switch means, indicator means connected to said DC lines, whereby should products of combustion be present an alarm is given by said alarm means and should the sensitivity of the detector be too high as established by the adjustment of the connection of the base of said one transistor means to said fifth impedance means an alarm is given by said alarm means or should said power lines fail an indication is given by said indicator means and said alarm is not given.

Claim 27

A fire detector adapted to be connected to a pair of AC power lines comprising rectifying means connected to said AC power lines for rectifying the AC power to DC power, said rectifying means having a pair of DC output voltage lines, filtering means connected between said pair of DC voltage lines, voltage regulating means connected to said pair of DC voltage lines, an ionization device having a target and chamber, first impedance means connected in series with said ionization device, the circuit of said ionization device and said first impedance means being in parallel with said voltage regulating means, sensor means, second and third impedance means connected in series with said sensor means, the circuit of said second and third impedance means and said sensor means being in parallel with said voltage regulating means and connected to said ionization device, fourth impedance means connected to one of said DC lines, first transistor means, second transistor means, said first and second transistor means having common emitters connected to said fourth impedance means, the collector of one of said transistor means being connected to the other of said DC lines, the base of said other transistor means being connected to the junction of said sensor means and said second impedance means, fifth impedance means connected between said DC lines, the base of said one transistor means being adjustably connected to said fifth impedance means for providing variable sensitivity of the detector to products of combustion, alarm means, switch means in series with said alarm means, said alarm means and switch means being connected to said AC lines, the collector of the other of said transistor means being connected to said switch means, indicator means connected to said AC lines, whereby should products of combustion be present an alarm is given by said alarm means and should the sensitivity of the detector be too high as established by the adjustment of the connection of the base of said one transistor means to said fifth impedance means an alarm is given by said alarm means or should said power lines fail an indication is given by said indicator means and said alarm is not given.

Claim 28

A fire detector adapted to be connected to a pair of AC power lines comprising rectifying means connected to said AC power lines for rectifying the AC power to DC power, said rectifying means having a pair of DC output voltage lines, filtering means connected between said pair of DC voltage lines, voltage regulating means connected to said pair of DC voltage lines, an ionization device having a target and chamber, first impedance means connected in series with said ionization device, the circuit of said ionization device and said first impedance means being in parallel with said voltage regulating means, sensor means, second and third impedance means connected in series with said sensor means, the circuit of said second and third impedance means and said sensor means being in parallel with said voltage regulating means and connected to said ionization device, fourth impedance means connected to one of said DC lines, first transistor means, second transistor means, said first and second transistor means having common emitters connected to said fourth impedance means, the collector of one of said transistor means being connected to the other of said DC lines, the base of said other transistor means being connected to the junction of said sensor means and said second impedance means, fifth impedance means connected between said DC lines, the base of said one transistor means being adjustably connected to said fifth impedance means for providing variable sensitivity of the detector to products of combustion, alarm means, switch means in series with said alarm means, said alarm means and switch means being connected to said AC lines, the collector of the other of said transistor means being connected to said switch means, indicator means connected to said AC lines, whereby should products of combustion be present an alarm is given by said alarm means and should the sensitivity of the detector be too high as established by the adjustment of the connection of the base of said one transistor means to said fifth impedance means an alarm is given by said alarm means or should said power lines fail an indication is given by said indicator means and said alarm is not given.

Claim 29

A fire detector adapted to be connected to a power source comprising voltage regulating means connected to said power source, an ionization device having a target and chamber, first impedance means connected in series with said ionization device, the circuit of said ionization device and said first impedance means being in parallel with said voltage regulating means, sensor means, second and third impedance means connected in series with said sensor means, the circuit of said second and third impedance means and said sensor means being in parallel with said voltage regulating means and connected to said ionization device, fourth impedance means connected to one side of said power source, first transistor means, second transistor means, said first and second transistor means having common emitters connected to said fourth impedance means, the collector of one of said transistor means being connected to the other side of said power source, the base of said other transistor means being connected to the junction of said sensor means and said second impedance means, fifth impedance means connected to said power source, the base of said one transistor means being adjustably connected to said fifth impedance means for providing variable sensitivity of the detector to products of combustion, alarm means, switch means in series with said alarm means, said alarm means and switch means being connected to said power source, the collector of the other of said transistor means being connected to said switch means, indicator means connected to said power source, whereby should products of combustion be present in an alarm is given by said alarm means and should the sensitivity of the detector be too high as established by the adjustment of the connection of the base of said one transistor means to said fifth impedance means an alarm is given by said alarm means or should said power lines fail an indication is given by said indicator means and said alarm is not given.

Claim 30

A fire detector adapted to be connected to a power source comprising voltage regulating means connected to said power source, an ionization device having a target and chamber, first impedance means connected in series with said ionization device, the circuit of said ionization device and said first impedance means being in parallel with said voltage regulating means, sensor means, second and third impedance means connected in series with said sensor means, the circuit of said second and third impedance means and said sensor means being in parallel with said voltage regulating means and connected to said ionization device, fourth impedance means connected to one side of said power source, first transistor means, second transistor means, said first and second transistor means having common emitters connected to said fourth impedance means, the collector of one of said transistor means being connected to the other side of said power source, the base of said other transistor means being connected to the junction of said sensor means and said second impedance means, fifth impedance means connected to said power source, the base of said one transistor means being adjustably connected to said fifth impedance means for providing variable sensitivity of the detector to products of combustion, alarm means, switch means in series with said alarm means, said alarm means and switch means being connected to said power source, the collector of the other of said transistor means being connected to said switch means, indicator means connected to said power source, whereby should products of combustion be present in an alarm is given by said alarm means and should the sensitivity of the detector be too high as established by the adjustment of the connection of the base of said one transistor means to said fifth impedance means an alarm is given by said alarm means or should said power lines fail an indication is given by said indicator means and said alarm is not given.

Claim 31

A detecting device as in claim 16, further comprising electric shield means around said chamber, said shield means being connected to said fifth impedance means for establishing a potential around said chamber.

Claim 32

A detecting device as in claim 22, further comprising at least one electric shield means around said chamber, said one shield means being connected to a portion of said device having a potential substantially that of said fifth impedance means.