The purpose of the G43 code is to tell the control that it needs to take into consideration the tool length that is stored in the tool length offset register. It will then add the amount it finds in that register to every Z axis move it does until G43 is cancelled ( with G49) or replaced with a new new G43 command for the next tool. G43 is used with an H code which identifies which offset to refer to in the offset page.
This critical features means that the individual tool length needs to be measured and added to the register before running the job. Without it the programme Z dimensions would have to be changed each time the job is run with new tooling to allow for the new tool lengths.
N1 T1 M6
N2 G0 G90 X0.Y0.M3 S4500
N3 G43 H1 Z50.