1. 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. 2. This product has a built-in 9V battery, and the cover can be opened to replace the battery. As shown in the principle diagram, if the red and black ends are not measured, the circuit is not conducting and there is no current consumption. 3. 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, . The product has a buzzer sound prompt, and the volume is about 100 decibels. It also has an indicator light prompt. Part name: 9V buzzer tester You can test whether the cable is normal, whether the wire is normal, whether the PCB board cable is normal, or whether the product is normal. Precautions: Do not use when the product is powered on or plugged in to a power source! Color: As Shown Material: Plastic+Metal Package Contents: 1 x Buzzer Tester Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.