Abstract: A new type of exchange system is disclosed which is suitable for the use in a facsimile communication system in which a large amount of information is transmitted in one direction, and the opposite direction has a small amount of information to be transmitted. According to the present invention, said large amount of information is transmitted using a circuit switching technique which assigns a fixed circuit to the forward direction to transmit said information, and a control signal or an acknowledgement signal in the backward direction from the receiving terminal, is handled through a packet switching technique in which a plurality of calls share a single transmission line or a time slot. Thus, a transmission line is used with the same efficiency as packet switching although information is transmitted mainly in one direction, and the switching load of the exchange is as small as in circuit switching.

Abstract: A new and improved stored program controlled electronic exchange system for a common channel signaling system through separate data links has been found. The control facility of said electronic exchange is shared by a common signal controller and a stored program type computer. The controller processes signals in said data links relating mainly to the transmission of signals such as serial-parallel conversion error control etc., while the computer processes signals relating to the copy of the transmitted signals. A common clock generator is provided for all data links for driving a plurality of MODEM's in said common signal controller and sending a signal in each data link in the same phase.Further, a pair of common signal controllers may be provided on a dual mode operation basis to increase the operational reliability.