ART Pro Audio SLA2 - 200W Power Amplifier - Manual (Page 8)

8
PROTECT INDICATOR LED
The LED will glow when the channel goes into protect mode. In protect
mode, the output signal to the speakers will be muted (channel
specific). If there is a fault condition at the speaker outputs (due to a
severe load or short) the LED will light until the fault is removed.
The protect lights will also light during power up and down, to indicate
that the signal is muted.