After the connection is created, the two sides can make a two-way transmission of both text message and files in all kinds of format.

It is concerned by more and more people. The two-way transmission technique of CATV by optical fibre is introduced and the design of the system is discussed.

The T104 test, used for two-way transmission loss measurements, far-to-near noise measurements and near-to-far noise checks is normally used in testing toll trunks.