To Cap and others who asked:

The schematic of the seismic preamplifier with the 4-pole
low pass Bessel filter can be found at:

http://www.eas.slu.edu/People/STMorrissey/index.html
under the section:
stmmisc.html "PSN INFO ... SLU Seismic Network"

I had previously posted the old 1980 pencil drawing, but about
a year ago I redrew it and updated some details. I just got
around to scanning the new drawing to the web page.

regards,
Sean-Thomas
__________________________________________________________

Public Seismic Network Mailing List (PSN-L)