http://www.iris.washington.edu/stations/seisWorkshop04/PDF/CompoundVertic= alSeismometer.pdf I just found this. If Mr. Peters, or anyone can = tell me more about this, please email me. http://www.iris.washington.edu/stations/seisWo= rkshop04/PDF/CompoundVerticalSeismometer.pdf =20 I just found this. If Mr. Peters, or anyone can tell me more = about=20 this, please email me. Thanks, Ted