Open USB FXS is a project that aims to deliver and offer to the community an open-hardware/open-software FXS board. The target mass-scale manufacturing cost would be in the order of $10.00, this low-cost being a critical overall design factor. The board will communicate to a host using USB. It is expected that the board will be possible to utilize by VoIP software such as Asterisk, when appropriate device drivers are built.

The board is built around two chips: a Silabs 3210, that implements all telephony functions, and a PIC (a 18F2550 for the time) that interfaces between the 3210 and the USB and implements the board's routine tasks, like passing around PCM I/O data. All the intelligence lies on the PC side, which drives the board by setting registers on the 3210 and performs audio I/O.