Trunk Line Three. Super high speed digital transmission line offering a total data-carrying capacity (bandwidth) of 44.736 million bits per second (Mbps) with 672 individual channels in the US version, 32.064 Mbps with 480 channels in the Japanese (J-3) version, and 34.368 Mbps with 480 channels in the European (E-3) version. T-3 and its variants require coaxial or fiber-optics cables or radio (microwave) media and cannot run on ordinary (unshielded twisted pair) telephone lines.