The May issue of Linear Technology Magazine has a schematic of a geophone
preamp using a two-wire interface.  The intention is that the preamp be
located with the geophone and require only a two-wire interface to provide
both power and signal.  The schematic and brief description is contained in
a design note available at 

http://www.linear-tech.com/pdf/dn230f.pdf


Karl Cunningham
La Mesa, CA.
PSN station #40
karlc@.......
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