Simtronics GD1 MK3 Operating Manual page 27

Check that the absolute transmission is as expected (indicated in the graph below). The
obtained absolute transmission can vary somewhat from detector to detector. If the
signal is significantly lower than the suggested values, this is an indication that the fine
alignment needs to be improved, the RX is poorly aligned or the lenses are dirty. The RX
is usually well enough aligned during the Coarse alignment, but this can also be a
reason for too low signal.
16
If the absolute transmission is acceptable click
DONE.
17
If the absolute transmission is significantly lower
than expected then also perform fine tuning for
RX in addition to the TX.
18 Click "Save".
GD1 Page 27 of 76 850-816926-EN R06