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

 Applies only to X.25 PVCs.  Identifies the logical channel number
 for the X.25 PVCs.  Specify a value in the range 0 to 4095.  This
 parameter is mandatory when you specify an X.25 PVC for the first
 time.