Google Duo was once reserved for Google Smart Displays with cameras. Now, that's changing, with Google rolling out Duo calling to non-display speakers, as well.
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It means older speakers like the original Google Home and the Google Home Mini have Duo support, but obviously the calls will be audio-only.
You'll also only be able to call and be called by users who have Duo on their phones, using the, "Hey Google, call [contact name] on Duo," command.
You can also call specific speakers in your home from your phone or another Google Home speaker by saying "call living room," or whatever you've named it.
You'll be able to ask Google to end the call, or simply tap the top of the Google Home or Home Max, or hit the side button of the Home Mini.
At the time of writing, the feature is in the very early stages of rolling out and clearly not yet fully functional.
Google says it's only working in the US in English, but there are reports of people in the UK getting it to work too (although these people may have the language on their devices set to US English).
So, if it's not working for you yet, have patience. In the meantime, here's how to set up Google Duo on your smartphone.