To attain proper traffic control even when a destuff cell is inserted in the traffic control for in-device cells and to conduct proper traffic control even when a layout of a traffic control circuit and a traffic control object differ.

The system has a traffic control circuit 7 provided with a traffic control section 8 that controls traffic of cells received by a speed conversion circuit 1, a time management section 9 that manages a time of the cells received by the traffic control section 8 and a selector that selects a cell outputted from the traffic control section 8 or a cell bypassing the traffic control section 8. The system has a mode where the traffic control section 8 stops its operation to allow a destuff cell to bypass the traffic control section 8 upon the receipt of the destuff cell and a mode where the traffic control section 8 receives all cells.