My question was how I could filter some traces through a digital low
Jan R. de Weille offered a routine in C . This was the kind of
answer I was looking for at first. But although used to write C code I
was not able to understand Jan's function. That is not Jan's fault
:). -- Thanks to Jan.
Matt Jones suggestion to use MATLAB  has drawn my attention to the
similar but freely available programm Scilab . Its documentation
"Signal Processing With Scilab" contains a detailed description of the
optimal use of a bundle of different digital filters. By the way: I
like to read Matt's competent articles in bionet.neuroscience.
 in article <37261DF8.FD99BDF1 at bigfoot.com>
 in article <7g506k$lu6$1 at fremont.ohsu.edu>