Controlling DPS PAR over 9600 baud serial connection from Genlocked Amiga

Here I am controlling a DPS PAR board in an Amiga 3000 from another Amiga (1200) running Term 4.8. The two Amigas are connected using a null-modem cable. The serial connection is running at 9600 8N1 with RTS/CTS.
The output of the Amiga 3000's PAR board is fed into the S-Video In of a Digital Creations SuperGen SX attached to the Amiga 1200. So, what we see in this video is Term's graphics on top of the S-Video output of the PAR board.
The Amiga 3000 is running a custom ARexx script which listens for commands over the serial port and feeds them to the PAR's "DDR" ARexx port. It then feeds back the result. If there was no result, because of an ARexx quirk, it feeds back the name of the variable, RESULT.
Note that the custom ARexx script is running with full tracing turned on, so is actually running at a fraction of the speed it would normally run at. This demo might have looked more impressive had I remembered to turn off tracing beforehand.