Sony SRS-BTS50 - Manual (Page 85)

Microphone
Note
If you received a call using your BLUETOOTH mobile phone, some
BLUETOOTH mobile phones may have handset use priority. In the case of the
HFP connection, talk on the system by pressing the (call) button on the
system for about 2 seconds, or using your BLUETOOTH mobile phone. For
details, refer to the manual supplied with your BLUETOOTH mobile phone.
To adjust the volume
Press the VOL +/– button.
The power indicator (green) flashes 3 times when set to the lowest or highest
volume level.
Tips
You cannot adjust the volume when not talking.
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