this description of some of the preferred embodiments will be aided by the referral to fig1 - 7 and tables 1 - 4 . in the sketches showing mct films , the thickness is greatly exaggerated and the scales are neither absolute nor relative . fig1 is a graph of a model of the ir transmission (%) versus wavenumber ( cm - 1 ) for the mct film composition ( hg . sub . ( 1 - x ) cd x ) te . the ir wavelength in μm is - 10 4 divided by the wavenumber . for graph 10 , x = 0 . 3 . for graph 12 , x = 0 . 25 . for graph 14 , x = 0 . 2 . the abscissa of the graph runs from a wavenumber of - 3500 ( corresponding to a wavelength of 2 . 9 μm ) to a wavenumber of - 500 ( corresponding to a wavelength of 20 μm .) the transmission percentages modeled are illustrative but less than actual because no anti - reflection coatings are assumed . the wavelengths 16 to the left of 10 ( 4 . 0 μm and shorter ) are absorbed by mct film 10 and , if electrodes are attached , an increase in conductance of 10 could be detected when emission in the 16 spectral region illuminates the mct film . conversely , wavelengths in regions 18 , 20 and 22 which are longer than 4 . 0 μm would be transmitted through film 10 and no change of conductance in 10 would be seen when illuminated at wavelengths longer than 4 . 0 μm within spectral regions 18 , 20 , 22 . the novel customization of mct ir detectors for specific wavelengths makes use of these physical properties . a preferred embodiment sketched in fig2 and described in table 1 shows a plurality of mct detectors 26 , 30 and 32 on a common substrate 34 . ohmic electrical contacts 28 are made by standard semiconductor processing techniques which are then attached to external sensing circuitry . to show the utility of such an embodiment , for the purpose of example , assume that 26 corresponds to an mct composition that detects all wavelengths shorter than 20 μm . to improve false alarm rates , detector 26 could be used as a general enabling signal for detectors 30 and 32 . assuming that 30 responds to wavelengths shorter than 4 . 0 μm and 32 responds to wavelengths shorter than 5 . 0 μm , we could easily determine if the component flame radiation contains a component between 4 . 0 and 5 . 0 μm . the detector configuration can be such to detect radiation on the detector side of the substrate or , with a transparent electrically insulating substrate such as cdte or cadmium - zinc - telluride ( cdznte ), radiation through the substrate could be detected . external optical filters and lenses can be used between the location to be monitored and the mct detectors for further enhancement if desired . table 1______________________________________id # function description alternates______________________________________26 detects ir at wavelengths hg . sub . 0 . 8 cd . sub . 0 . 2 te any wavelengthof 20 μm and below . film band for compositions of hg . sub . ( 1 - x ) cd . sub . x te with x from 0 . 1 to 0 . 9 . 28 ohmic contacts hgte film30 detects ir at wavelengths hg . sub . 0 . 7 cd . sub . 0 . 3 te any wavelengthof 4 . 0 μm and below . film band for compositions of hg . sub . ( 1 - x ) cd . sub . x te with x from 0 . 1 to 0 . 9 . 32 detects ir at wavelengths hg . sub . 0 . 75 cd . sub . 0 . 25 te any wavelengthof 5 . 0 μm and below . film band for compositions of hg . sub . ( 1 - x ) cd . sub . x te with x from 0 . 1 to 0 . 9 . 34 substrate for epitaxial film cdte orgrowth , ir transparent or cdznteopaque . substrate . ______________________________________ a detector assembly composed of vertically stacked mct detector films is sketched in fig3 . for the purpose of illustration , this topology assumes that substrate 42 is transparent to ir . mct film 40 has no ohmic contacts and is used as an optical filter having an mct film composition that absorbs wavelengths shorter than , say , 5 . 0 μm and passes all wavelengths longer than this . film 39 is cdte which is ir transmissive but is an electrical insulator . this prevents the changes of conductance of mct film 40 from affecting the detected conductance of mct film 38 . mct film 38 has a composition that detects all wavelengths shorter than , say , 6 . 0 μm . electrodes 36 coupled to external electronic circuitry will sense an increase in conductivity when radiation between 5 . 0 and 6 . 0 μm is passed through the substrate 42 . there can be a plurality of such pass - band ir filter detectors on a common substrate , placed either vertically or side - by - side or both , for the detection of specific ir wavelengths , forming a comb filter , either for the purpose of spectroscopic analysis , control or safety alarms . the range of alternate compositions for the mct films 38 and 40 are shown in table 1 . fig4 ( a ) shows a graph of the ir radiation spectrum of a gasoline fire in a normal atmosphere . an mct detector assembly designed for high performance in the detection of gasoline fires is sketched in fig4 (( b ). the materials of composition are shown in table 2 . ir radiation 44 is transmitted through transparent substrate 42 with little attenuation . the x in the mct composition of ( hg . sub . ( 1 - x ) cd x ) te for the optical filter film 46 is chosen to pass all wavelengths longer than about 1 . 5 μm and reject shorter wavelengths . the electrically insulating , ir transparent film 39 passes the remaining ir energy without altering the electrical conduction properties of mci film 50 . the mct composition for detector film 50 is chosen to increase its conductance when exposed to wavelengths lower than about 3 . 5 μm . thus the combined response of 42 , 46 , 39 and 50 are such that an increase of conductivity is observed between the two ohmic contacts 48 attached to 50 when the ir radiation 44 contains spectral components between about 1 . 5 and about 3 . 5 μm . from fig4 ( a ) it can be seen that this is the broad band of the ir spectrum of a gasoline fire . film 50 is separated from 54 by another ir transparent , electrically insulating film 39 . while 50 responds to ir radiation in the about 1 . 5 to about 3 . 5 μm band , it also optically rejects these wavelengths . the mct composition of mct detector film 54 is chosen to increase its electrical conductivity when exposed to ir wavelengths lower than 4 . 5 μm . the resulting response of 42 , 46 , 50 and 54 is such that an increase of electrical conductivity is observed between electrical contacts 52 when ir radiation 44 contains wavelengths between about 3 . 5 and about 4 . 5 μm . as can be seen from fig4 ( a ), 3 . 5 to 4 . 5 μm encompasses the conspicuous co 2 emission peak . therefore the detector assembly of fig4 ( b ) is uniquely tuned to respond to gasoline fires . table 2______________________________________id # function description alternates______________________________________42 substrate for epitaxial film cdznte cdtegrowth , ir transparent . 46 rejects ir wavelengths hg . sub . ( 1 - x ) cd . sub . x te filmbelow 1 . 5 μm and passes with x chosen for alonger wavelengths . 1 . 5 μm knee . 48 ohmic contacts to 50 . hgte any metal for ohmic contacts . 50 increases electrical hg . sub . ( 1 - x ) cd . sub . x te filmconductivity when exposed with x chosen for ato ir radiation below 3 . 5 μm knee . 3 . 5 μm and passes irradiation at longerwavelengths52 ohmic contacts to 54 . hgte any metal for ohmic contacts . 54 increases electrical hg . sub . ( 1 - x ) cd . sub . x te filmconductivity when exposed with x chosen for ato ir radiation below 4 . 5 μm knee . 4 . 5 μm______________________________________ fig5 ( a ) shows the ir spectrum from a bunsen burner flame supplied with natural gas in a normal environmental atmosphere . fig5 ( b ) is a sketch of a composite detector made from mct films ( whose compositions are described in table 3 ) stacked vertically to detect the combustion of natural gas . the ir radiation 44 from the flame passes through the transparent substrate 42 to an optical filter mct film 56 whose composition is chosen to reject all wavelengths below about 2 . 2 μm and pass all longer wavelengths . ir transparent , electrically insulating . table 3______________________________________id # function description alternates______________________________________42 substrate for epitaxial film cdznte cdtegrowth , ir transparent . 56 rejects ir wavelengths be - hg (. sub . 1 - x ) cd . sub . x te filmlow 2 . 2 μm and passes with x chosen for alonger wavelengths . 2 . 2 μm knee . 58 ohmic contacts to 60 . hgte any metal for ohmic contacts . 60 increases electrical hg (. sub . 1 - x ) cd . sub . x te filmconductivity when exposed with x chosen for ato ir radiation below 3 μm 3 μm knee . and passes ir radiation atlonger wavelengths62 rejects ir wavelengths be - hg (. sub . 1 - x ) cd . sub . x te filmlow 4 . 2 μm and passes with x chosen for alonger wavelengths . 4 . 2 μm knee . 64 ohmic contacts to 66 . hgte any metal for ohmic contacts . 66 increases electrical hg (. sub . 1 - x ) cd . sub . x te filmconductivity when exposed with x chosen for ato ir radiation below 4 . 8 μm knee . 4 . 8 μm______________________________________ layer 39 separates film 56 from 60 to preserve the electrical conductivity of mct detector film 60 . the composition of 60 is chosen to increase its electrical conductivity when exposed to ir at any wavelength below about 3 μm . as a consequence of the physical characteristics of 42 , 56 and 60 , an increase of electrical conductivity will be seen between electrical contacts 58 when the ir radiation 44 contains spectral components from about 2 . 2 to about 3 μm . ir radiation of longer wavelengths than about 3 μm is passed by the ensemble of 44 , 56 and 60 . another electrically insulating , ir transmissive films 39 separate 60 from 62 and 62 from 66 such that changes in electrical conductivity of 62 do not effect the electrical characteristics of either 60 or 62 . the ir optical filter mct film 62 has a composition that rejects all wavelengths lower than about 4 . 2 μm and passes all longer wavelengths . the mct detector film 66 has a composition that increases its conductivity when exposed to ir radiation at wavelengths shorter than about 4 . 8 μm . this composite structure results in an increase of electrical conductivity between contacts 64 when ir radiation 44 contains spectral components from about 4 . 2 to about 4 . 8 μm . thus the composite detector shown in fig5 ( b ) has two spectral response peaks , one at 2 . 3 to 3 μm and the other at 4 . 2 to 4 . 8 μm which can be seen from fig5 ( a ) to be dominant in the spectrum of a natural gas flame . thus the detector described in fig5 ( b ) and table 3 is uniquely suited to the detection of natural gas combustion . fig6 ( a ) is a graph of the combined ir spectrum of the compounds water and co 2 . since both of these compounds always appear in the combustion of any organic product , a detector which responds independently to h 2 o and co 2 should have great utility in the implementation of fire detection , analysis and control . fig6 ( b ) and table 4 describe an embodiment of such a combustion detector . because the two ir regions relating to h 2 o are relatively broad , a composite mct film detector 83 of vertically stacked films will be used for the detection of h 2 o . the spectral peak of co 2 is much sharper so that a separate detector 90 is placed laterally on the same on the same ir transparent substrate 42 . the ir radiation 44 passes through substrate 42 encountering mct filter film 78 whose composition is chosen to pass only ir wavelengths longer than about 2 . 5 μm . electrically insulating , optically transparent films 39 are used in all cases to prevent any cross talk between stacked films . mct detector film 76 has a composition that increases conductivity when exposed to radiation shorter than about 2 . 8 μm and passes all ir wavelengths longer than this . electrical conductor 72 connects detector film 76 in series with detector film 70 . mct optical filter film 74 has a composition that rejects all wavelengths shorter than about 5 . 0 μm which includes the band associated with co 2 . mct detector film 70 has a composition that causes increased electrical conductance when exposed to ir wavelengths shorter than about 8 μm . this configuration results in ir detector 83 exhibiting an increase in conductance between electrical terminals 80 and 82 when exposed to ir radiation from a fire in which h 2 o is a component . table 4______________________________________ alter - id # function description nates______________________________________39 ir transparent , electrically cdznte cdteinsulating film . 42 substrate for epitaxial film cdznte cdtegrowth , ir transparent . 70 increases electrical conductivity hg (. sub . 1 - x ) cd . sub . x te filmwhen exposed to ir radiation at with x chosen for awavelengths below 8 . 0 μm . 2 . 5 μm knee . 72 ohmic connection to connect any suitable metaldetection films 70 and 76 inseries . 74 rejects ir wavelengths below hg (. sub . 1 - x ) cd . sub . x te film5 . 0 μm and passes ir at longer with x chosen for awavelengths . 5 . 0 μm knee . 76 increases electrical conductivity hg (. sub . 1 - x ) cd . sub . x te filmwhen exposed to ir radiation at with x chosen for awavelengths below 2 . 8 μm and 2 . 8 μm knee . passes longer wavelengths . 78 rejects ir wavelengths below hg (. sub . 1 - x ) cd . sub . x te film2 . 5 μm and passes longer with x chosen for awavelengths . 2 . 5 μm knee . 80 , ohmic connections to 70 and 7682 respectively . 84 ohmic connections to 86 . any metal for ohmic contacts . 88 rejects ir wavelengths below hg (. sub . 1 - x ) cd . sub . x te film4 . 2 μm and passes ir radiation with x chosen for aat longer wavelengths 4 . 2 μm knee . ______________________________________ because 70 responds from about 5 to 8 μm and 76 responds from about 2 . 5 to 2 . 8 μm and 70 and 76 are connected electrically in series by 72 . to avoid spectral attenuation and diffusion of the narrow band of ir radiation associated with co 2 , it was deemed good practice to fabricate detector 90 as a separate entity on the same substrate . ir radiation 44 passes through substrate 42 encountering mct filter film 88 which has a composition to reject all wavelengths below about 4 . 2 μm . electrically insulating , ir transparent film 39 isolates the electrical properties of 88 from 86 . mct detector film 86 has a composition which increases the conductance between terminals 84 when exposed to ir wavelengths shorter than about 4 . 8 μm . this composite h 2 o and co 2 low false alarm , flame detector is suited to a wide variety of applications including fire detection in forests , homes , warehouses , factories and so on . the relative intensities of the ir radiation from these two compounds could also be used for industrial control applications . another embodiment of this invention relates to the ratios of co to co 2 in air or oxygen fed flames used in industrial manufacturing and in internal combustion engines . oxygen starved combustion will contain a higher percentage of co than a properly fed flame . fig7 ( a ) is a graph of the ir spectrums of co and co 2 combined . fig7 (( b ) is a sketch of a composite detector used to sense both of these combustion products . since the co 2 detector is identical to the one shown in fig6 ( b ) it will not be further described . the co detector 96 is of similar structure except for the composition of the mct films . ir radiation 44 passes through ir transparent substrate 42 and encounters optical filter film 94 . the x of the composition of 94 , hg . sub . ( 1 - x ) cd x te , is chosen to reject all ir wavelengths below 4 . 4 μm and pass all longer wavelengths . ir transparent , electrically insulating cdte film 39 electrically isolates 92 and 94 without appreciable attenuation of the ir radiation . detector film 92 has a composition hg . sub . ( 1 - x ) cd x te with x chosen to cause an increase the conductance between electrical connections 91 when exposed to ir radiation at wavelengths shorter than about 4 . 8 μm . thus ir detector 96 responds to the ir emission wavelengths of co as a combustion product . through the use of external electronics and computer components one may use the responses from detectors 90 and 96 to regulate air or oxygen flow in smeltering operations in foundries , etc . as well as to examine exhaust products of internal combustion engines . while this invention has been described with reference to illustrative embodiments , this description is not intended to be construed in a limiting sense . for illustrative purposes , specifically tuned sensors and geometric arrangements have been chosen for clarity without in any way intending that these examples limit the generic application of mct ir detectors operated at an uncooled temperature to detect , analyze and control the gaseous products of combustion . the example applications are intended as prototypical and not limited to those included . many more detectors than two can be placed on the same substrate . an analytic instrument such as an ir spectroscope would contain numerous mct detectors of variously tuned wavelengths . various modifications and combinations of the illustrative embodiments , as well as other embodiments of the invention , will be apparent to persons skilled in the art upon reference to the description . it is therefore intended that the appended claims encompass any such modifications or embodiments .