D4 Digital Channel Bank Family: Dataport-Channel Units for Digital Data System 56-kb/s Rate
B. J. Dunbar, D. V. Gupta, M. P. Horvath, R. E. Sheehey, S. P. Verma · Bell System Technical Journal · 1982
Increasing demand for high-speed data services makes it desirable to give more customers access to the Digital Data System (DDS). To provide service at 56 kb/s, the highest DDS rate, “dataport” channel units have been developed to extend DDS network channels over T-carrier lines, using D4 terminals. These 56-kb/s dataport units offer a flexible and economical arrangement for serving smaller cross sections of data subscribers, and make use of a coding scheme for error correction that makes special selection of lines (for error rate) unnecessary. We describe the design of 56-kb/s dataport units, while articles referenced herein discuss dataport system questions and the design of lower speed dataport units.