1.Five-levels volume adjustments Level 1 for the patients with mild deafness Level 2 for the patients with mild and moderate deafness Level 3 for the patients withmoderate deafness Level 4 for the patients with moderately severedeafness Level 5 for the patients with severedeafness 2. More Tips for Using This Device 1) If you hear howlingnoise, please make sure you have inserted the earplug correctly and using the proper size. 2) Please don't use this device for a long period of time with high volume. It could damage your hearing. 3) Please keep you device clean at all times to avoid damage or blockage of your earplugs and receivers. 4) Do not use while showering or swimming, it is not waterproof. Avoid long exposure to sun or heat. 5) Keep away from kids and pets. 3.Hearing Amplifierspecifications Max OSPL: =128(±3dB) HFA OSPL: 106(±4dB) Max Full-ongain(FOG): 28(±5dB) Maxgain: 43(±5dB) Equivalent input noise: =29(±3dB) THD: =7 Percent ±3 Percent Frequency range: 300Hz-4000 Hz Chargingtime: 5-7h Working time: 12-16h 4. Each packageincludes ? 1×Hearing Amplifier ? 1×Instruction Manual ? 1×Cleaning Brush ? 1×Storage Case ? 1×USB Charging Connector ? 1×Adapter ? 3×Earplugs