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

    Default: 500

    Minimum time, in milliseconds, between the assertion of data set
    ready and accepting a call by asserting request to send. This
    characteristic is not supported if the characteristic modem
    control is none.