BenQ T420 User Manual page 37

Touch Feature
The adjustment of the Clock Frequency, Phase, H Position and V Position settings is only
required when the Auto Adjustment function does not work perfectly on certain input signals.
When turned on, Input Resolution, Aspect ratio, PIP, Clock
Frequency, Phase, H Position, V Position, Overscan and Display
Wall will be disabled to optimize touch performance.
This feature is only available for VGA, DVI and HDMI inputs.
The OSD (On-Screen Display) menu 37