Library /sys$common/syshlp/nclhelp.hlb show, modem_connect, line, Interchange Circuits, RS-449 Circuits  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    Modem Connect Line Interchange Circuits

    NCL Attribute Name    Circuit     Description
    ----------------------------------------------------------------------

    carrier detect        RR          Receiver Ready

    clear to send         CS          Clear to Send

    data set ready        DM          Data Mode

    data terminal ready   TR          Terminal Ready

    local loopback        LL          Local Loopback

    remote loopback       RL          Remote Loopback

    request to send       RS          Request to Send

    ring indicator        IC          Incoming Call

    signalling rate       SI          Signaling Rate Indicator
    indicator

    signalling rate       SR          Signaling Rate Selector
    selector

    test mode             TM          Test Mode