Siemens SIMATIC LOGO! CMR2020 Operating Instructions Manual page 20

Connectors and LED display
2.3 LEDs to display operation
Meaning of the LEDs
LED
All LEDs
L
Power supply
P1
LAN
R
Signal strength (mobile wireless)
F
Error
20
Status
Flashing
Lit
Not lit
Off
On
Flashing
Lit green
Part flashes yellow and
part lit green
Off
Lit green
Lit yellow
Off
Flashing
OFF
ON
Meaning
Fatal error
Firmware being updated
No voltage present or applied
•
Device shut down
•
No external power supply connected
Power supply connected
Initialization or reconfiguration active
Link
Data
No link or no cable connected
Very good
Medium
No signal
Data
No error
Error (see also "Error LED lights up red" (Page 132))
Operating Instructions, 09/2014, C79000-G8976-C356-01
LOGO! CMR2020 / LOGO! CMR2040