GENERAL NOTES
SUMMARY OF XSF FLAGS
XSF1 -  If set, allows detector 4 to call & extend CØ if its presence timer is expired
GENERAL OPERATION
If going from CØ -> BØ, substitute AØ yellow for CØ yellow
DETECTOR OPERATION
If XSF1 is set, then allow detector 4 to call & extend CØ if its presence timer is expired