Ok, it seems nobody knows TTl or Rs232 protocol. Well, can so someone suggest another way to control Beosystem 3 via domotic system? For example, can soleone explain what is the "Ir-in 9 pin"  and the "IR 1+2" on the rear panel? I am thinking i can use the Lintronic 238 but first of all i want to know every connection and how can these be used. Thank you very much for any reply.

Hi emabonacchi I found following (see attached) Indeed, the RS232 and ttl are referred to Hotel Setups where the features are not known to me; further, the monitor socket seems to be needed for BV4 or BV9, the IR1,2 could be for IR blaster to the projector, and the CINEMA socket seems to be the appropriate one for the control I have to add, I am no expert and cannot further help. BTW: your English seems quite good to me ;-) (I am also not a native speaker)

ps: however, https://archivedforum.beoworld.org/forums/t/41508.aspx Stefan tells, that CINEMA seems not to be rs232 but seems to control certain projector models/brands

This link might help with the protocols https://github.com/nigels0/Beosystem-3-control-non-B-O-TV Stoobie