Traffic control system for asynchronous transfer mode exchange

An asynchronous transfer mode switching system for receiving a cell from a corresponding one of a plurality of input highways and for outputting the cell to a selected one of a plurality of output highways, for each of a succession of cells, each cell having a corresponding discard characteristic and being assigned a corresponding priority order, selected from a range of plural, different priority orders, comprising:

• buffer units, each operable for avoiding interference of the cells by temporarily storing a cell received from a corresponding input highway before outputting the received call to the selected output highway, the number of said buffer units being the same as the number of said input highways from which a received cell may be output to the selected output highway;
• cell accumulation measuring means, operatively connected to each of said buffer units, for measuring the amount of cells accumulated in said buffer units;
• cell discarding means, operatively connected to said buffer units and to said cell accumulation measuring means, for discarding a cell with an assigned low priority order, relative to the range of plural, different priority orders, when the measured cell accumulation amount exceeds a predetermined cell accumulation amount;
• and
• said buffer units being connected with a read-out multiplexing control line through which a token, which provides permission for reading out a cell, is circulated, said cell discarding means, further, in response to the arrival interval of the token exceeding a predetermined token arrival interval, discarding a cell with a priority order which is low, relatively to the range of plural, different priority orders.