Experimental 224 Mb/s PCM Terminals

During the late 1950's, the feasibility of pulse code modulation for the transmission of voice over cable pairs was established, 1 and sincc 1962 there have been substantial installations of such equipment. More recently, attention has been focused on extending P C M to much higher bit rates and to long-haul, toll quality systems. This effort has produced experimental 224 M b / s PCM terminals capable of transmitting broadband signals such as television and mastergroups of voice channels with a signal quality that meets Bell System transmission objectives. High-performance, high-speed terminals having provision for all major functions required in a commercial system were constructed in order to demonstrate the applicability of P C M to the broadband, longhaul network. Satisfactory solutions to all the major technical problems associated with high-speed P C M terminals have been demonstrated. Two important results of the studies are: the feasibility of 1813 1818 T H E B E L L SYSTEM T E C H N I C A L J O U R N A L , N O V E M B E R 1 9 f i a