A universal serial bus (USB) type C transmission line includes a host-to-host bridge, a first multiplexer, and a second multiplexer. When a first device and a second device are coupled to the first multiplexer and the second multiplexer respectively, the first multiplexer determines whether the first device is a host or a slave device and the second multiplexer determines whether the second device is another host or another slave device, and the first device optionally communicates with the second device through the host-to-host bridge, the first multiplexer, and the second multiplexer, or through the first multiplexer and the second multiplexer according to determination results of the first multiplexer and the second multiplexer.