This document summarizes various electrical testing instruments. It describes probes and indicating devices that detect conditions but do not provide accurate measurements. It also describes multi-meters, which combine multiple functions in a single unit to provide accurate measurements, and specialty testers that conduct more specific functions precisely. Continuity testers, voltage testers, outlet testers, multi-scanners, wire tracers, circuit breaker finders, analog and digital multi-meters, clamp meters, and infrared thermometers are all discussed.