Data communication apparatus having communication-mode changeover

Abstract

In an ISDN network, data communications can be performed in two communication modes corresponding to line and packet switchings in the same network. The line switching is effective in transmitting mass data to a receiving station and receiving the same therefrom at high speed, and accounting is made to a period of time required for communication in a public network. On the other hand, the packet switching is effective in transmitting low-speed data or small amounts of data produced in a discrete manner, and accounting is made to the amount of transmitted data in the public network. With a valve toward making efficient use of the two communication modes, the present invention relates to a data communication apparatus of the type wherein the two communication modes are changed as needed so as to perform data communications, and to a data communication system suitable for use with the data communication apparatus. In other words, a means for performing data communication continuously over two calls is provided so as to change one communication mode to another under data communication based on a user's request. Thus, when the amount of creation of data varies appreciably under communication, data communication is made based on the optimal communication mode determined according to the amount of creation of the data.