This is a user-submitted tutorial for configuring the Grandstream HT486 ATA with Google Voice Gateway. Thanks Mark!
The Grandstream HT 486 has several quirks. Some of which may relate to the infrastructure to which it is connected; modem/router and Internet provider.
My tests found that DNS SRV records works in SOME cases. in other cases I either has a hissing (or raining) sound in phone calls or the dial tone became a 2Khz tone . Interestingly enough sometimes the same HT486 that had these issues in one place, with the same configuration, would work when connected to a different provider/Infrastructure. If you have any of these problems, your ATA is not broken it is a bug apparently, as I have installed many of these and always run into it. I show the configuration here with DNS SRV disabled for the bugs in the HT486.
I have always had to use STUN on these devices as seen here.
I always set specifically only the codecs I want to use.
There appear to MANY issues with some Cisco Cable modems and HT486 as follows;
DHCP sometimes fails. If this is the case you can reset the modem but sometimes a fixed IP will work but other times not.
I was unable to get the Cisco modem to assign a fixed (via MODEM DHCP SERVER) IP to the HT486. The HT486 always behaved as if it had no IP.
When answering the ringing GVGW line as the phone rings you try to answer and get a dial tone. This MAY be related to security settings in the Cisco modem. Disable security reboot everything and test again.
See the attachment for an example configuration.