PURPOSE: To attain quick recovery from an abnormal state by providing 1st, 2nd exchange switches, a means selecting only a priority cell and 1st and 2nd selection means and applying only the priority cell to 2nd and 1st exchange switches in a standby system.
CONSTITUTION: A cell priority identification circuit 13 discriminates a priority / non-priority cell in the normal operation and applies only the priority cell to a 1 system ATM switch 16. A 0 system ATM switch 12 and the switch 16 use a means for monitoring the capacity of a FIFO (first-in first-out) buffer basically so as to control the cell in a way that the cell of a definite length received from the FIFO buffer in the ATM network does not overflow. That is, cells of both priority / non-priority types are applied to the switch 12 in the active system and only the priority cells are applied to the switch 16 and subjected to exchange / transmission therethrough. The switch in the standby system applies exchange but no output therefrom is applied to a demultiplexer 15. Thus, the priority cell exchange / transmission in the abnormal state is much ensured.
HAJIKANO KAZUO
SOMIYA TOSHIO
