may be its not compatible with cordless yet... try using regular phone..
I've purchased a USB adapter that connects to a cordless phone. It is very similar to the RJ11 internet VOIP phone Adapter. It basically routs a signal from a cordless phone to the computer through the headphone and mic ports as well as a USB slot. While using the phone near the computer, the volume control works well and the peripheral behaves perfectly. The problem is when one wants to wander away from the computer with the cordless phone. The person on the other end experiences two very interesting problems; the first is that the volume they can hear from the person talking decreases extremely quickly which can be countered by turning up the volume on the computer (To a point), and the second is that small noises very far away from the phone are picked up extremely loudly. In other words while the person could yell into the phone and you couldn't hear them, you can literally hear a clock ticking from a different room. I've tested multiple phones and have determined that they are not the problem and the computer's volume control does very little to help with the second problem. To me it seems as if the adapter itself is mixing up which sound signals it is deciding to amplify and which to reproduce quietly. Any insight as to what could be done about this (types of drivers, other adapters, etc) would be extremely appreciated. Thank you in advance.