Keith Saunders: Having reviewed the Service manual it is clear that only the transmit and receive signals are wired on the RS232 and other signals such as dataset ready are not wired which means that any polling or data update will NOT occur by justing plugging the cable back in. Actual data must be sent to the Beovision 4 to change its mode, as the cable was unpluged at switch on of the Beosystem, the signal would have been sent, but clearly not received.
So, in answer to your question I would say this is working as per the design.
Kieth, I am not sure that this fully answer my question. I am a poor man so I can not effort to buy the full system so I have managed to get hold of a Beosystem 2, which I would try to use with an non B&O screen.
By monitoring the serial output I can I see that at the start up (e.g TV ON) a series RS232 commands are send to the screen. This commands are all identical to Panasonic RS232 commands.
However after this sequence is send from the Beosystem the system locks/hangs (picture muted, but RGBHV synchronisation is there) as the screen was waiting for the "callback" from the Plasma Display Panel(PDP). In the panasonic documentation this is actually described - where every transmitted command to the PDP is returned as a "callback" with same structure as the original command.
However, by my question I just wanted to clearify that the behaviour of my Beosystem 2 was corrret (and the unit was not broken) - before spending a lot of time trying programming the litlle "juicy"system.
However, I guess that you have already answered me indirectly - if the Beosystem 2 just would start up without any "callback" from the PDP then much more people would have been using and discussing it in here !