Rolton K600 7.4V Bluetooth Audio Speaker Megaphone Voice Amplifier Without Transmitter, Without Transmitter Color:Black it needs to be recalibrated

it needs to be recalibrated before use)

The primary components include the coil

3 cm) for Feng Shui/Travel

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Exterior Chamber: MS powder coated

Rolton K600 7.4V Bluetooth Audio Speaker Megaphone Voice Amplifier Without Transmitter, Without Transmitter Color:Black it needs to be recalibrated1. K600 Bluetooth amplifier, no button, can not insert the card, can not be inserted into the U disk playback, only the amplifier function 2. Note: the need to achieve the wireless function to be equipped with a separate transmitter or wireless microphone. 3. Easy to wear, can be buckled in the belt or pants on the edge of the belt can also be used to hang waist belt, can be freely adjusted 4. Bluetooth 5. 0, compatible with the connection of