I need a modem diagram

Greetings, All!

Thanks to everyone who responded to my letter about ZX-Net.
Now another _OOHuge_ request: someone throw a modem circuit at me or at the echo
. Judging by the information received, I am interested in the circuit diagram of a modem called
Vicomm, preferably with its modifications.
And I also read in the 26th issue of ZxNew that a new modem called
XTR-modem has appeared, which is better than its predecessor both in speed and in capabilities,
so I am interested in whether it is possible somehow contact its developers about implementing and using it in Voronezh (since they are talking about the fact that it will supplant Vicomm).
As always, I will be glad to receive any information on this issue.

Sincerely, Dmitry