I agree with Guy that you might need to go the ML ->1611 way to get an input with some kin of datalink that you might be able to communicate with.
A couple of source regarding datalink:
1.
Article on the Beotech section on this site: https://beoworld.org/beotech/datalink.htm
The linked datalink manual linked to on that site is not availebale there, but can be found in the manuals section if you upgrade your membership.
2.
A readme file for some Github projects regarding datalink. https://github.com/toresbe/datalink
he refers to it as datalink 80 and datalink 86. As far as I have found out datalink 80 is also what B&O call Audio Link which is the communication used between a Beomaster and tape/CD/phone. Datalink 86 is then what’s called Audio Aux Link which is the communication between Beomasters and Beovisions or in this case the 1611 converter.
As for how the inner workings of the communications work I have no idea, but hope you can get something out of these sources.