JTS RU-901G3 Instruction Manual page 13

Indicators
Green
Flashing green
Red
Alternating red and green
Blue
Flashing blue
Others
Battery charging is supported. The transmitter turns off automatically when
charging.
When battery is < 1.8V, the transmitter will turn off automatically.
If the microphone is turned off with the mute switch on mute, just slide the
switch up to turn the microphone on.
Battery > 2V
Microphone mute
Battery ≤ 2V
Microphone mute (and battery low)
Pairing successful
Data receiving error
LED
10