The red protection LEDs for Rotel amplifiers can behave slightly differently depending upon the design of the amplifier in question. 

On class AB models, such as RB-1582, RB-1552 and RMB-1506, the protection LEDs will click on briefly then turn off whenever the power amplifier is powered up or powering down into standby mode. For example, when using the 12V trigger to power the amp on or off, the LEDs will briefly turn on to signify the amp is now on. When the system is turned off the protection LEDs will again turn on briefly when the amp shuts down. 

On class D models such as RB-1572, RB-1562, RB-1510, RMB-1565, RMB-1575 or RMB-1512 the red protection LEDs will remain lit whenever the amplifier is powered down into standby mode. This is the case when using the 12V trigger to power the amplifiers on or off; the red protection LED will remain lit whenever the system is off, and will go out when the amplifiers are powered up. Note that in either case if the power amplifiers are turned off via the front panel power button all of the front panel LEDs will be off. The above circumstances refer to using either 12V trigger or signal sense modes to control power to the amplifiers.

The protection LEDs for Rotel amplifiers will also of course light up if the unit has experienced a fault and is in fact in protection mode. In this case the LED should remain lit at all times.