Sennheiser EM 500 G2 Instructions For Use Manual page 41

"MUTE" display
The "MUTE" display appears on the display panel and the backlighting of
the standard display switches from green to red. In addition, the text "MUTE"
flashes in alternation with the standard display when
the RF signal of the received transmitter is too weak,
the received transmitter has been muted (with the pilot tone transmission
or evaluation activated).
Modulation display
The level display for audio signal "AF" shows the modulation of the received
transmitter.
When the transmitter's audio input level is excessively high, the receiver's
level display for audio signal "AF"
When the transmitter is overmodulated frequently or for an extended period
of time, the text "PEAK" (backlit in red) flashes in alternation with the
standard display.
shows full deflection.
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