A couple of videos I’ve recently posted include demos of the regenerative loop interface board I’ve made for the Model 15 family of machines. Demos in the first video show half duplex (local) operation, full duplex with a PC via serial/USB port with full ASCII/Baudot conversion, Baudot pass through mode, and finally, AFSK decoding (e.g., ITTY feed). Skip to about 7:40 in the video to go directly to the interface board demos.
In the second video, the interface board allows use of the Model 15 as a console terminal for an Altair 8800 computer running CP/M. No changes to CP/M or the Altair were required. This video demonstrates how the interface deals with ASCII characters that are not present on the Model 15 but are required for computer operation.