Increasing the Capacity of the No. 4A Crossbar

The capacity of switching networks in carried load is limited by the percentage of calls which fail to find a path (matching loss). Clean, reliable data on carried load and first and second trial matching loss have recently been made available. These data, from a heavily loaded No. 4A Crossbar System, have been analyzed to find the effect of load balance and have been compared with theoretical predictions. The results are: (1) the carried load limit for No. 4A Crossbar has been increased seven percent; (2) the effect of poor load balance has been quantified; (3) second trial performance is better understood; and (4) more precise administrative rules have been written so that machines can operate successfully at the new higher load level.