VMS Help TCPIP Services, TELNET, TN3270 Keyboard Functions, NUM_OVR  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    VT100: EXT + J              VT200: Remove
    DEFINE_KEY Function: NUMOVR

    Lets you enter nonnumeric characters in to numeric fields. Once
    you enable this function, use NUM OVR again to disable it. If you
    do not disable the numeric lock override, it remains enabled even
    after you exit from TN3270. The letter O appears on the status
    line to indicate that the numeric lock override is in effect.