Yealink SIP-T48G Administrator's Manual page 703

Parameter
None
To configure dual headset via web user interface:
1. Click on Features->General Information.
2. Select the desired value from the pull-down list of Dual-Headset.
3. Click Confirm to accept the change.
Sending volume allows user to adjust the sending volume of currently engaged audio
devices (handset, speakerphone or headset) when the phone is in use.
Note
It is not applicable to CP860 IP phones.
Procedure
Sending volume can be configured using the configuration files.
Configuration File
Permitted Values
<y0000000000xx>.cfg
Configuring Audio Features
Default
Configure the sending
volume of the speaker.
Parameter:
voice.handfree_send
Configure the sending
volume of the handset.
Parameter:
683