3. This product has a built-in 9V battery, and the cover can be opened to replace the battery. if the red and black ends are not measured, the circuit is not conducting and there is no current consumption. 1.The product has a buzzer sound prompt, and the volume is about 100 decibels. It also has an indicator light prompt. 2. How to use: After plugging in the test , touch the two ends of the measured wire. If an audible and visual alarm is issued, it means that the wire is conducting, otherwise it is not conducting. 4. After the measurement circuit is turned on, the loop current is about 20ma. This product is not suitable for measuring tiny electronic components, electronic circuit boards, etc., Weight: 0.51477938177 pounds, Manufacturer: tiyao