Abstract: Auto-adaptive filtering devices for analysis and treatment or processing of A.F. signals.These devices are characterized in that they include filtering means splitting the applied signals into two parts or channels having complementary spectra, a first channel being considered as error channel to determine a function of versus predetermined criteria, the transmission of the other channel and to react on the positioning of the cutoff frequencies of the filtering means.Main applications being noise reducers, band-reduction devices, devices for speech analysis and synthesis.

Abstract: A noise reducer for multi-channel stereophonic signals is characterized by separate processing channels having different characteristics for the main and composite signals with means to reconstitute the phase correspondence between the signality processed separated in the two channels.

Abstract: A D.C. amplifier for low-level currents includes an input stage having first and second cascode mounted transistors and a bis circuit adapted to maintain the base and collector potentials of the first transistor very close to each other over a predetermined temperature range. The amplifier is particularly suited for use in a flame detection device and, in addition, may include a protection circuit for the base-emitter junction of the first transistor.