Extron Electronics VTG 400D_400 DVI User Guide - Manual (Page 84)

Appendix, cont’d
VTG 400D/400 DVI • Appendix A-20
Hum Bar Detect Pattern Video Levels
Background (Adjustable between 0% - 100%)
+4%
+6%
+2%
+4%
+2%
+4%
+6%
+2%
+4%
+2%
–4%
–6%
–2%
–4%
–2%
Note: All bar levels are given relative to the background video level.
28. Hum Bar Detect
The Hum Bar Detect pattern assists the user with the location and
evaluation of low level ground loop type signal interference. Visual
results of induced or conducted low-level AC currents can be difficult
to see, depending on image material. This pattern consists of a flat
field with three groups of shallow horizontal steps. Each group contains five steps
in increments of 2%.
The upper and lower groups ascend/descend in value (+2%, +4%, +6%, +4%, +2%)
and the middle group descends/ascends in value (-2%, -4%, -6%, -4%, -2%).