Scientific, optical, measuring, signaling, checking, regulating apparatus and instruments, namely, flue gas and process gas measuring and analyzing systems comprising measurement sensors and probes, gas analyzing sensors and probes, gas sampling probes, and high temperature thermocouples; optical gas measuring systems comprising optical sensors and probes; optical signal devices, namely, electronic displays, [ CRT displays, ] LED displays, and LCD displays; acoustic signal devices, namely, electronic sound reproducers, [ loudspeakers ] and electronic sound generators; apparatus and instruments for conducting, switching, transforming, accumulating, regulating or controlling electricity, namely, electrical and pneumatic controlling devices, electric transformers, and electrical conductors; apparatus for recording, storing, transmission and reproduction of sound, images and data; recording carriers and storage media for sound, images, and data, namely, pre-recorded, writeable and re-writeable magnetic and optical recording data carriers; data processors and computers; all of the afore-mentioned goods for measuring and analyzing the composition of gases