j5 create JUA250 - USB 2.0 HDMI Display Adapter - Manual (Page 51)

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Off
When Off selected, it will disable
the display of the USB HDMI
Display Adapter.
Identify Monitor
When Identify Monitors is
selected, a serial number will be
shown at the upper right corner of
attached display device.
You can use the Hotkey function
to find out the serial number of
each display.