Do not depend on software lockouts to prevent equipment damage and do not expect software lockouts to give you an ironclad guarantee of compliance with contest rules!
Visible light communication (VLC) is a data communications variant which uses visible light between 400 and 800 THz (780–375 nm). VLC is a subset of optical wireless communications technologies.
Extreme QRPp using the KX2, KX3, K3, or K3S
Wayne Burdick, N6KR
Power output on the KX2, KX3, K3 and K3S can be set as low as 0.1 W directly using the PWR control. However, you can actually set power output to much lower levels (< 1 milliwatt), with fine control, by turning off ALC in the menu and adjusting the drive level manually.