Panasonic VL-V900 Installation And Operating Instructions Manual page 59

5.10.4 Extension box indicators
Category Meaning
Normal operation Idle
Call or monitoring in progress
Error DIP switch 4, 6, 7, or 8 is in the
"on" position
POWER (green)
Lit
Lit
Lit
5. Programming
ACCESS (red)
Off
Lit
Flashing slowly
59