Has anyone heard of the "Zollner" seismograph or horizonal pendulum 
seismograph utilizing the Zollner suspension. I understand that it solves the 
boom piviot problem by using two wires which are kept in tension.  Therefore, 
there is no boom pivot contact and hence no friction.  Has anyone built one 
of these?  How does it compare to a Lehman seismograph?
Jim Allen
Cerritos, Calif.

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