The Modem Connect module implements one of the protocols in
    the Physical layer described by the Digital Network Architecture.

                                NOTE

    For Tru64 UNIX, the WAN Device Drivers are provided as an
    installable subset within the product HP Wide Area Network Support
    for Tru64 UNIX.  You must install this subset before you can refer
    to the modem connect module entities in an NCL command.

    For OpenVMS, you must install the WAN Device Drivers from the
    HP X.25 for OpenVMS product before you can refer to the modem
    connect module entities in an NCL command.