I've been using a Gigaset A580IP VoIP phone base station with two handsets, an A58H and a C610A, for a few years now. I'm set up with three providers, Faktortel, 2talk, and VFX. Both 2talk and VFX work flawlessly when selecting any codec except G.722. Faktortel is just there as a backup pre-paid service and I rarely use it.

The problem arises when I set G.722 as the codec for either 2talk or VFX. The sound quality is phenomonally good when I call the voicemail service of both providers, but when pressing DTMF tones, I get a sharp and brief electrical crackling sound (almost like accoustic feedback). This occurs most of the time on both handsets and using both providers. On odd occasions, the sound occurs without me pressing anything on the keypad. If I switch back to G.711, the problem goes away (and the voice quality is not nearly as good).

Has anyone come across this problem, and more importantly, found a solution?

Cheers,

David.