Sony DR-BT21iK Mode D'emploi page 17

Notes
 To listen to music from the headphone jack of the iPod, disconnect the
transmitter from the iPod.
 While the transmitter is turned on, it consumes power from the iPod. We
recommend disconnect the transmitter from iPod when not using the Bluetooth
function.
 If the headphone is connected to the iPod while the iPod is playing back, it
consumes power from iPod.
 If you turn off the transmitter while the iPod is playing back, iPod will power off.
 It is not recommended to turn off iPod as the linkage will lost between the
transmitter and the Bluetooth receiving device.
 There is no need to charge the transmitter as it will receive power from the connected
iPod. It is recommended to check the iPod's remaining battery before using.
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