CONTENTION CONTROL SYSTEM

PURPOSE:To prevent a packet exchange to send a packet continuously by providing a means placing a lower priority on a packet exchange acquiring the transmission right in a system where plural packet exchanges use a transmission line in common. CONSTITUTION:When a transmission data from a register 3 of its own equipment takes place, a contention control signal is sent to an E line 17 to apply the contention control. Since the E line is subject to wired OR connection in other equipment, the contention control signal outputted serially is subject to contention discrimination by a contention discriminator 1 in the unit of bits. Thus, a priority control section 2 is used to generate a pattern placing lower priority for each acquisition of the transmission right, thereby suppressing the consecutive packet transmission of an optional equipment.