Voltage detectors have visual, audible, or vibration indicators that sense the presence of voltage. Handheld non-contact voltage detectors (NCV) do not contact test objects directly to indicate voltage. Voltage testers contact test objects and have visual, audible, or vibration alerts that indicate live circuits. Continuity testers verify the presence of voltage and are often used to test breaker panels, switches, and outlets. Absence of voltage testers (AVT) install into equipment and visually indicate when lines are de-energized and safe to work on. Accessories pair with compatible detectors and testers to expand functionality and improve performance.