What does full duplex mean?
The ATIS Telecom Glossary defines duplex operation as transmission that is possible simultaneously in both directions of a telecommunication channel, also called full-duplex or two-way simultaneous operation. Half-duplex operation allows both directions, but only one at a time, like a walkie-talkie where you hold a button to talk.
A system can behave half duplex even on a full-duplex line. In a VoiceXML phone application, a prompt with barge-in turned off doesn’t take in what the caller says while it plays, so the caller has to wait for it to finish.
Full-duplex voice AI applies the idea to the model. OpenAI describes GPT-Live as full duplex: it can listen and speak at the same time, so apps should update the caller’s and the assistant’s captions separately while both are talking.
Example: while the agent explains a setting, the caller says “yes, found it”. A half-duplex system misses it until the agent stops, while a full-duplex one hears it as it’s said.
Why does full duplex matter for a voice agent?
Natural conversation overlaps. People interrupt, say “mm-hmm” and correct themselves mid-sentence. An agent that only takes strict turns talks over these moments or misses them, and the call feels like a walkie-talkie.
Full duplex brings its own work. The system must not mistake its own voice, echoed through the caller’s speakers, for speech, and it has to judge which overlapping sounds are real interruptions. Echo cancellation and interruption testing matter more than they do with push-to-talk.
How does Kawl Now handle full duplex?
Kawl Now calls are full duplex from end to end. The WebRTC connection carries the visitor’s microphone and the agent’s voice in both directions at once, and the agent runs on OpenAI’s GPT-Live, which can listen while it speaks. There’s no push-to-talk: the microphone stays open until the caller mutes it or ends the call.
Live captions show both speakers’ words, and the transcript is saved as text. The widget asks the browser for echo cancellation, so the agent’s voice from the speakers is less likely to be heard as the caller.
Interruption handling hasn’t yet been verified in a recorded test with a person speaking into a browser microphone, so try talking over the agent during your own tests.
Common questions
What is the difference between full duplex and half duplex?
Full duplex carries signals both ways at the same time, like a phone call. Half duplex carries them both ways but one at a time, like a walkie-talkie, so one side has to stop before the other can be heard.
Is WebRTC full duplex?
Yes. A WebRTC connection sends and receives audio at the same time, so two people, or a person and an AI agent, can be heard at once. Whether the conversation feels full duplex also depends on the software at each end.