Library /sys$common/syshlp/ncphelp.hlb SET, CIRCUIT, INACTIVE BASE base  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 Applies to DDCMP CONTROL circuits. This value indicates the base
 priority of an INACTIVE tributary after the tributary has been
 polled.  You can indicate a separate base for each of the
 indicated polling states.  Base must be a decimal integer from 0
 to 255.  The default is 0.