I have read many posts remarking on the difficulty making sense of the Radio Shack Pro-106 User's Guide. IMHO, many of the problems with the RS Pro-106 manual are ones of "omission" rather than "commission". There seem to be many dead ends and incomplete explanations in the Radio Shack version. I have found the GRE owner's manual for the PSR-500 to be more complete, more logical in layout, and more comprehensible. It is available for download in the support area of the GRE America website. GRE America, Inc. Note: there are some nomenclature differences between the RS and GRE systems, e.g., "Signal Stalker" vs. "Spectrum Sweeper".