Enables or disables headset prior feature.
If it is set to 1 (enabled), a user needs to
press the HEADSET key to activate the
headset mode. The headset mode will not
be deactivated until the user presses the
HEADSET key again.
Enables or disables dual headset feature.
If it is set to 1 (Enabled), users can use two
headsets on one phone. When the IP
phone joins in a call, the users with the
headset connected to the headset jack
have a full-duplex conversation, while the
users with the headset connected to the
handset jack are only allowed to listen to.
Note: It is not applicable to SIP-T19P and
SIP-T21P IP phones.