Asynchronously (independently) with the main headWB1, SB1, SB11 activates the left group.
WB2, SB2, SB12 activates the right group
WB3 activates both the left and right group at the same timeSB10 nulls SB11 and SB12 (do not make holes).
Inserting SB10 as the first step in a program, you are sure that the horizontal groups are immediately "armed", and lowered ready for boring.
NOTE: SB1 = SB11 and SB2 = SB12