OOPS.
I did some more reading of the geotools site and realized that I made a bad assumption about the data format. The information is transmitted in an analog format not digital. So the tone is simply FM modulated with the amplitude of the output from the seismograph. This means that if there is no movement of the seismograph you will see a tone at the center frequency of the channel. The frequency of the tone will follow the level of the seismograph signal up and down within the limits of +/- 125 Hz. Full scale + volts would be a tone 125 Hz greater than the center frequency and full scale - volts would be a tone 125 Hz less than the center frequency. 

Jim Hannon

--
Jim Hannon
http://www.fmtcs.com/web/jmhannon/
42,11.90N,91,39.26W
WB0TXL
--
__________________________________________________________

Public Seismic Network Mailing List (PSN-L)