Abstract: A wireless digital personal communications system (or PCS) having a plurality of intelligent base stations and portable handset terminals, each having a predetermined radio cell coverage area. The radio cell, radio-telephone PCS has a full ISDN interface. The personal communications system facilitates direct interconnection and switching of PCS call traffic through the ISDN interface and the public switched telephone network, or any switched network. The personal communications system has voice/data/image (or any combination thereof), and incoming and outgoing calling capability. The PCS is fully operational and compatible with any modulation approach selected The intercell protocol hand-off being provided through distributed logic which is implemented in software that is resident in the intelligent portable handset terminals, in the intelligent base stations, and in the public switched telephone network (or any switched network).

Abstract: In the public switched telephone network, an originating modem can identify an answering modem, e.g., as to the type of modem it is, by detection of a low-level identification signal sent from the answering modem. The low-level identification signal is hidden within an industry standard "answer tone," e.g., a CCITT V.25 answer tone of 2100 Hz. If the low-level identification signal is detected by the originating modem, the industry standard "handshaking" procedure is terminated and a non-standard handshaking procedure is implemented. If the identification signal is not detected by the originating modem, the industry standard handshaking procedure is simply completed.