Specifications Clear Sound 4 batteries free Max sound output: 130±5dB Sound gain: ≥50dB Total harmonic wave distortion: ≤10% Frequency range: 300~4000Hz Input noise: ≤30dB Voltage: DC 1.5V Current: ≤4mAUsage Open the cartridge cover, and put the battery in the correct position. Zine Air battery is the best choice and has a longer life. Before using, ensure power is turned off, or make the volume “l”. Put the ear hook on your ear, and plug in the ear tightly. Note: The unit is on & off position, and the volume is on “l”, otherwise the instant sound will make you uncomfortable. Turn the power, and adjust the sound volume to get clear sound, If you hear whistling, please check whether you have plugged in the earplug tightly. If it can’t be plugged tightly, please change the other size plug
