  Results of a search for Kr-78 double K-capture with the large low-background
proportional counter (2005-2008 years) at the Baksan Neutrino Observatory are
presented. An experimental method and characteristics of detectors are
described. Basic features of the digitized pulses processing using wavelet
transform are considered. With due account taken of the analysis of individual
noise characteristic it has been shown that the appropriate choice of both
wavelet characteristics and sequence of processing algorithms allows one to
decrease the background in the energy region of useful events with a unique set
of characteristics by ~2000 times. New limit on the half-life of Kr-78 with
regard to 2K-capture has been found: T_{1/2} >= 2.4E21 yrs (90% C.L.).
