Sennheiser 3000 series Instruction Manual page 10

The SKM 3072, SK 50 and SK 3063
transmitters transmit a battery status
D4
signal.
When 20 to 30 minutes battery life
remains, the receiver display shows
"LOW BATT" (D4).
If squelch is activated "MUTE" will
light, and the "LOW BATT" will extin-
guish. It will relight when a signal is
received from the transmitter.