Sennheiser SpeechLine Manual page 66

SL Rack Receiver DW
flashes yellow:
The firmware is being updated.
lights up red:
No radio link to a transmitter. In addition, the background of
the display panel changes back and forth between light and
dark and No Link appears on the display panel.
flashes red:
The accupack capacity of the received transmitter is only suf-
ficient for max. 30 minutes of operation.
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