Abstract: A line switch including a concentrator arrangement for coupling telephone calls between a plurality of subscriber lines and a plurality of port group highways to a central office switching network in a telephony system. The analog voice signals are first digitized and multiplexed into time slot channels on line group highways for transfer to the concentrator arrangement. The concentrator arrangement couples the digitized voice information signals between time slot channels on any of the line group highways and any of the port group highways. The line switch includes control circuitry that selects the time slot channel, line group highway and port group highway to couple the digitized voice information signals between the subscriber line and the central office matrix switch through the concentrator.