Omron NT-series Operation Manual page 256

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NT600S Symptoms
Buzzer sounds, RUN LED
is OFF.
Touch panel does not
respond
PC mode changes to
monitor mode.
Cause
Malfunction due to external noise.
Malfunction due to external noise
Touch panel is broken.
The NT600S changes the mode
during host link communication.
Remedy
Distance the communication cable from the source of
the noise and insert a noise filter in the power supply
line.
Distance the communication cable from the source of
the noise and insert a noise filter in the power supply
line.
Check the touch panel by performing the touch panel
test in the I/O check in the maintenance mode.
This is normal with the NT600S specification. When
using a PC that can also be connected using the NT
link, connect it with the NT link (the mode is not
changed when using the NT link).
Section 7-1