HD voice: what devices are supported?

[etad putta]

I live in the mpls area and just made a call to the daughters iphone 6 with the wifes iphone 6. The clarity was amazing! Not sure what other devices are compatible, but it was very, very clear. Cool stuff, hope it comes to all phones and areas soon!!..AT&T HD Voice

 

[etad putta]

More info...Report: AT&T's VoLTE-based HD Voice exceeds 3G voice, Skype in terms of quality - FierceWireless