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

    Default: 30

    Maximum time, in seconds, that the entity will wait for indication
    of a successful call before disconnecting the line. This
    characteristic is supported only when the characteristic modem
    control is none.