F-999B is a high-sensitivity microphone, an earpiece with strong metal detection capability, and a perfect high-quality earphone with high sensitivity and good quality. Built-in lithium battery and FM mitter function, easy to operate and easy to carry. Operation method: Insert the earbuds into the headphone jack, insert the probe into the microphone jack, turn the volume/clockwise switch, the power indicator light is on, adjust the gear abc gear knob, and select the best effect. F-999B also has FM mission function, the antenna is inserted into the FM socket, this function is automatically turned on, and the mission frequency: 100m. All-metal body, fine workmanship, professional high-end precision inst ents and equipment. Superior performance, clear sound quality, high sensitivity, imported components. Four-speed adjustment to meet different conditions of use. The built-in FM radio mission module can mit the signal to the wireless remote control. With the expansion of the jack, additional functions can be performed on external devices.<br><br>Note: Pay attention when charging, the charging indicator light is on, and the fully charged indicator light will automatically turn off, please charge to avoid burning the machine. The probe must be in static contact with the surface of the tube. Please do not drag the probe in parallel to avoid damage to the probe. Press the ABC button to adjust the probe for the best effect, and the volume knob to adjust. Use the probe scroll buttons, do not move the file on the volume buttons. Product Specifications Consumption: Current: 10 mAh Use Battery: 3.7v Rechargeable Lithium Battery; 800 mAh The fourth audio option: a file (200hz) b (800hz) c (1200hz) d (probe) Probe sensitivity: -70db, the highest audio amplification: 20000 times Through: cement pipe steel pipe This product is used for construction site construction, vehicle mainten