This user’s workflow is actually very common.
When temporarily leaving their workstation, they use the KVM Switch’s Lock mode to lock the system. In their mind, this action represents a “complete departure”—the screen should go blank, and the monitor should behave as if the signal has been disconnected, automatically entering sleep mode.
However, the actual experience was slightly different.
After entering Lock mode, the screen immediately went black, but the monitor itself remained powered on and did not enter sleep. When the same monitor was connected directly to the computer without the KVM, it behaved correctly and entered sleep as expected.
This comparison clearly pinpoints the boundary of the issue: The monitor is fully functional, the system’s power management is working normally, and the difference occurs solely in the signal behavior introduced by the KVM.
From “Black Screen” to Signal Behavior
The engineering team fully reproduced the scenario.
After Lock mode is triggered, the observable outcomes are:
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Lock key takes effect
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Video output stops
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The monitor shows a black screen
From the user’s perspective, this seems like a complete “leave desk” action.
However, further examination at the HDMI signal level revealed a subtle difference. In Lock mode, the KVM stops transmitting valid video frames, but the HDMI link itself is not fully disabled. The TMDS clock signal may still be present, either as residual clocking or low-level noise.
Why the Monitor Doesn’t Sleep
For some monitors, entering sleep mode is not determined solely by the presence of video content. It also depends on whether the HDMI link is detected as active. When the monitor detects an ongoing TMDS clock, even without valid video data, it may interpret the situation as:
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A source is still connected
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The current black screen is only a “blank display,” not a “no signal” state
As a result, the monitor stays on rather than sleeping.
This explains why direct connection works normally, while KVM Lock mode produces a different behavior.
Adjusting from Logical Black Screen to Physical Disconnect
Once the mechanism was understood, the solution focused on signal behavior itself. Firmware was updated so that when Lock mode is triggered:
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HDMI video output is completely turned off
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All link signals, including the TMDS clock, are stopped
From the monitor’s perspective, this is equivalent to unplugging the HDMI cable—a true “no signal” state. In this state, the monitor can follow its power-saving logic and naturally enter sleep mode.
Change in User Experience
After the firmware update, the user tested the same workflow again:
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Trigger Lock mode
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Monitor recognizes no signal
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Enters sleep as expected
The entire process now aligns with the user’s expectations without additional intervention.
Through this firmware improvement, the KVM’s Lock function now works reliably across all types of monitors. This not only solves the immediate problem, but also demonstrates a rigorous approach to product design—every feature should behave as intended and remain dependable in real-world usage.
