Profile: William B. Johnson & Assocs. develops telescoping survey meters and quartz fiber pocket dosimeters. We provide radiation safety products. This microprocessor-controlled instrument represents the new gold standard of survey instruments. The GSM-500 is a digital instrument with an analog display that automatically chooses the correct range with no user intervention required. Portable portal monitor is a full color touch sensitive graphics readout which makes it easy to set up and operate. It includes audible and visual alarms, many diagnostics, & 120 vac w/10hr battery backup. Our GSM-500 auto-ranging survey meter is a digital instrument with an analog display that automatically chooses the correct range with no user intervention required.