Abstract: A dual telephone capable of performing and receiving calls via PSTN or via an IP based connection by using a single communication set. A user may select to call either via PSTN or IP from the communication set. In preferred embodiments the telephone has a base-station that is connected via an air-interface, e.g. DECT based, to a communication set. The base-station provides a PSTN interface and a USB interface for establishing IP based telephone connection via a USB port on an associated PC with Internet connection. The telephone may be provided with a program to run on the PC, this program providing an interface to a Softphone program provided by a softphone provider. According to a preferred USB protocol, auxiliary data messages, e.g. control messages, can be sent via the USB HID interface that allows exchange of e.g. Internet services such as emails to be retrieved by the communication set. Telephone audio data are exchanged via USB audio class data.