Lexus LS460 Owners Book page 510

3-5. Using the hands-free system (for cellular phone)
Status display
You can check such indicators as signal strength and battery charge on
the "Phone" screen.
Indicators
Connection status
Battery charge
Call area
Signal strength
508
Connection status
Battery charge
Call area
Signal strength
Conditions
Blue: Good
Yellow: Bad
: Not connected
Full
"Rm": Roaming area
"Hm": Home area
Excellent
Empty
Too bad