Hello, Tried to get some good and clear answers at the Siemens forum, decided to try here aswell. I have a setup with 12 G120C inverters and three gas burner units on a profibus line. If I unplug any of the devices will I of course get an error from the loaded OB. But, now and then can I lose the connection to two or more of the inverters without any notification. It seems that the communication is up and running, but the don't respond to any commands. The normally green LED on the inverters switch over to flashing red when they stop to respond. They will also show fault code 1910. I am using standard telegram 20, this is also set in the inverters parameter lists. Another funny thing is that the fault bit in the status word is always set. Even when the inverters don't hav any faults or alarms. ZSW looks like this (with or without response from the inverter): Bit 0 = 1 (Ready for switching on) Bit 1 = 1 (Ready for operation) Bit 2 = 0 (Running) Bit 3 = 1 (Fault) On all the time, even when there is no faults in the inverter Bit 4 = 0 (No coast down active) Bit 5 = 1 (No fast stop active) Bit 6 = 1 (Switching on inhibited active) Bit 7 = 0 (Alarm present) Bit 8 = 1 (Speed setpoint - actual value deviation within tolerance) Bit 9 = 0 (Control requested) Bit A = 0 (f or n comparison value reached) Bit B = 0 (I, M or P limit not reached) Bit C = 1 (Reserved) Bit D = 1 (No motor overtemperature alarm) Bit E = 0 (Direction of motor rotation) Bit F = 0 (Display CDS) Anything I might have missed or done wrong ?