PURPOSE: To mutually communicate between terminals without passing through a network terminating set by establishing a link using a communication channel and controlling the using right of an information channel using a signal access protocol layer between an object terminal and its communication destination terminal.

CONSTITUTION: First, since plural terminals TE1 to TE3 are connected to one bus line 1, the link is established, for example, between the TE1 and the TE2, between which a communication is to be executed. A communication (D) channel is used for establishing this link. This D channel controls the detection of a collision, and no problem occurs even the respective devices TE1 to TE3 simultaneously send signals. After the link is established, the using right of an information (B) channel is acquired using a signal access protocol layer 3. Thus, the communication between the devices TE1 and TE2 can be executed. Only the terminals, for which the link is established, can use the B channel, and not only the transfer of the data such as a packet but also the transmission of a sound signal can be executed by using this B channel.