The Gamecom 777 is an analog, stereo headset that uses 3.5 mm plugs. However, it comes packaged with a Dolby USB sound card. The Dolby sound card plugs into the headset and connects it to a computer's USB port. And it virtualizes 5.1 surround sound.
Included in the package is a USB Surround Sound adapter. On that adapter are two Dolby algorithms, Dolby Pro Logic II and Dolby Headphone. All audio comes into the adapter as 2 channel stereo via USB from the computer. That audio is then passed off to Dolby Pro Logic II. Dolby Pro Logic II takes the Left and Right channel content and using the directional cues that occur naturally in stereo creates a five-channel surround output representing the left, right, center, left surround and right surround channels. This information is then passed off to Dolby Headphone which emulates the 5 channels over a standard 2 channel stereo headset.