Honeywell MX9 Reference Manual page 216

Because of the cumulative effect, and using the Battery Power Scheme Defaults listed above:
The backlight turns off after 3 seconds of no activity,
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The display turns off after 18 seconds of no activity (15 sec + 3 sec),
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And the device enters Suspend after 5 minutes and 18 seconds of no activity.
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If the User Idle timer is set to Never, the power scheme timers never place the device in User Idle, System Idle or
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Suspend modes.
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