After 2 months of testing, this product is entirely satisfactory. OVH configured with a VOIP account, the connection is perfectly stable and of good quality. However, prefer the g729 codec for slow connections or overloaded; it is much more robust to packet loss at the expense of a slight decrease in audio quality. I added a combined A510H: no compatibility issues, just perfect. Note that with 2 handsets, you can simultaneously call landline and IP line. If you opt for the orange free messaging services (3103), the system can recognize the orange notification signal and flashes a red LED on the handset associated with a message waiting. In short, buy eyes closed.