Where it can be used? It's perfectly used in the water or special work environment, such as underwater training spot or swimming center and surfing on the water. With the little gadget the couch do not have to shout at the trainee all the time, Its absolutely easy to use, just speak to your trainee or partners with the normal voice-volume to the boxes or the earphone What's bone conduction? Sound are decoded and converted into vibration on facial bone! directly received by cochlea----bypass eardrum. No electric-Magnetic wave. In general, we believe listening to humans voice or the sound of music with ears only. But with the technology, the voice& sound generally transmitted by bone vibration, described as the bone conducted sound. Advantage 1,Let ear absolutely free at the same time, you can still enjoy your normal conversation and listening to the surrounded sounds without removing the bone conduction headset 2,Hearing aid and protection, ok for people with hearing loss and impairment, and help prevent hearing deduction/loss 3,Even in high noise condition, you can hear the clear sounds by the use of ear plugs for the protection 4,perfectly used in the water or special work environment Function introduction: Suitable for entertainment enjoyment in life under the water Through a wireless host may lead various formats music Under the water by means of a bone conduction, the closed state change in the water, children can get refreshing and fatigue resistance In bad listening environment he can improve the security of command It is underwater coaching assistants, solve past call things that break the throat Applications: swimming, underwater exploration, underwater ballet, deaf and dumb school sailing Parameters: Modulation: FM Receiver sensitivity: -113dBm Input sensitivity: < 200mv Noise-signal ratio: > 82dB Distortion rate: less than 0.7% Audio FM between: 20Hz to 20kHz Loudspeaker: bone conduction transducer 10 meters under water work Receiving distance: in 120M Power supply voltage:3.7V DC Port: built-in mini DC port Size:65mm(L)x46mm(W)x12.5mm(H) Net weight:55g Receiving sensitivity:-5dbu Remark: this item contents only 3 frequency-modulations only and can be up to 7 FMs, one walkie talkie can speak to 15pcs headset(select the light with same color in using) Blister packing with 4 color printed backcard,with English instruction,GW:210g/pcs,packing size: 20cmx10cm