I have recently gotten my hands on an old, used Risograph GR 1750. It is in working condition and prints like a charm. In the manual it mentions on page 58 (see image below) that it is possible to connect the Risograph to a PC. Unfortunately, it does not specifiy how this is done and the mentioned additional manual for the »Risograph Computer Interface System« is nowhere to be found.

Is anyone informed enough about this old machine to help me out and explain to me how I can connect it to a PC?

Manual Page 58