This invention discloses a system, device and method for transmitting both non-video signals and video signals between different communication interfaces. The system includes a first communication interface, a buffer module, a second communication interface, and an emulator module. The first communication interface is coupled to an electronic device, for transmitting a first differential signal and a first auxiliary signal. The buffer module is coupled to the first communication interface. The second communication interface is coupled to the buffer module, for transmitting a second differential signal. The emulator module is coupled to the second communication interface via a hub. The emulator module receives a second auxiliary signal. Data exchange for the first auxiliary signal and the second auxiliary signal is performed via the second communication interface between the buffer module and the emulator module.