"Enter PhaseIV Address"

    A DECnet-Plus system may or may not use a DECnet Phase IV style
    node address. A node address of 0.0 indicates that this system
    will be communicating with DECnet-Plus nodes only. If your network
    contains some systems running DECnet Phase IV, you may want to
    specify a compatible address in order to communicate with them.
    If your network consists solely of DECnet-Plus and/or OSI systems,
    this may not be required.

    The DECnet Phase IV node address consists of an area number
    (between 1 and 63), and a node number within the area (between
    1 and 1023).

    Enter the PhaseIV address you want to use, or enter 0.0 if you
    want to communicate with DECnet-Plus nodes only.