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For spike microphones and such there are two methods of defense, easy and hard. The easy way is to set of some kind of noise generator to mask the sounds and do a physical search of the outside of the building w/ a linemans induction pickup. If the mike's are using cable (not rf or you would have found them w/ the spectrum analyzer) then you should hear the signal at some point. The hard way (assuming they are sending the signal in some other way other than rf or land line, say a pwm laser) is to get yourself a set of IR goggles and check the place out.
Most camcorders can see IR normally and have an IR filter that sometimes can be removed. Turning off the lights will help.
Hope this helps....
Have a Merry Christmas
sdw -- Stephen D. Williams Local Internet Gateway Co.; SDW Systems 513 496-5223APager LIG dev./sales Internet: sdw@lig.net CIS 76244.210@compuserve.com OO R&D Source Dist. By Horse: 2464 Rosina Dr., Miamisburg, OH 45342-6430 GNU Support ICBM: 39 34N 85 15W I love it when a plan comes together