This hack was put together by reader [Forrest Cook]. He was wondering if there were any radioactive materials in his rock collection. This is an add-on box for a 60s era Victoreen CDV700 Geiger counter. Vintage gieger counters don’t actually count; they use an analog meter with an integrator circuit to do short term averages. Forrest’s box plugs into the headphone jack of the Geiger counter and does true digital counting with a Motorola microprocessor. The signal could also be sent to a computer with a little modification. He did find a handful of radioactive rocks, but nothing that was serious enough to worry about.