1. Function Definition: A portable device used to detect the presence of working voltage on electrical equipment.

2. Categories: Low-voltage Testers, High-voltage Testers.

Low Voltage: Test pens, pocket-sized testers. Swivel-angle type, folding type, test pens, etc. High Voltage Testers: Including GDY (GSY) high voltage testers, GDY.Ⅲ (original GD type) high voltage testers, GDY-F rainproof high voltage testers, GDYC windmill-type high voltage testers, (pY-s rope-type high voltage testers, and YD language-type testers. DC Testers, DC digital testers, AC digital testers. 3. Composition: Composed of two parts: the test indicator and the telescopic insulating rod. Optionally, add a handgrip for three parts.