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

    Support: All
    Default: 55            Value: 1-65535

    Period, in seconds, for which an X.25 call remains connected
    after being established, irrespective of traffic. This should be
    set small enough that the call is cleared before the start of the
    next charging interval. This attribute is supported only if the
    characteristic type is x25 da.