Vizio XVTHB100 - Quickstart Guide - Manual (Page 11)

Voice dial: Press Talk and say your programmed keyword. To use voice dial, your phone must support this feature.
Redial: Press and hold Talk. The phone dials last number you called.
Answer a call: Press Talk.
Reject a call: While the phone is ringing, press and hold Talk. The call is sent to voice mail.
Hang up: While in a call, press Talk. The active call is disconnected.
Answer a second call: While in a call, press Talk. The active call is placed on hold. The second call is connected.
Reject a second call: While in a call, press and hold Talk. The second call is sent to voice mail.
Answer or swap held call: Press Talk to answer the held call and disconnect the active call.
Mute/unmute microphone: Press and hold both Volume Up and Volume Down. The microphone will not work while muted.
Swap a held call: While in a call with a call on hold, press and hold Talk. The active call is swapped with the call on hold.
Adjust call volume: Press Volume Up or Volume Down.
Swap audio between
phone/headphones:
While in a call, press and hold Talk. The audio output is swapped from the headphones to the phone.
To swap back to the headphones, press and hold Talk again.