Use the default settings. If you are in uk then they have no relevance.

"George" <geodabass@hotORNOTmail.com> wrote in message
news:dbns9u$hbq$1@news.freedom2surf.net...
> I'm using a Grandstream 486 ATA. Does anyone know what difference Onhook
> Voltage and FXS Impedance make? I've tried changing them, and have
> noticed to change at all.
>
> Thanks
>
> George
>
>