A network access device (NAD) is comprised of a data set for coupling to a data communication trunk, a trunk control unit (TCU) connected with the data set, a trunk control interface (TCI) connecting the TCU to an internal data bus, an internal memory, a microprocessor control and a device interface...http://www.google.fr/patents/US4430702?utm_source=gb-gplus-shareBrevet US4430702 - Network access device
