I need OS9 help Please

I'm trying to run an older digital scan back that's tethered to my old G4 running OS9.2 Tiger. OS9 is necessary to run this camera,. X won't work. Between the G4 and the scan back is the scan back's mini computer that receives sends info between the G4 and the scan back. I replaced the mini computer's hard drive, as it was dead. It's now starts up very hopefully, and I'm now trying to initialize it with the scan back diagnostic data via the G4. For initialization a modem serial port is needed to send data from the G4 to the mini computer. I'm using a Keyspan twin serial adapter that plugs into a free USB port on the G4, and then via port 2 on the Keyspan, to a serial cable that goes to the mini computer. The Keyspan twin's control panel is set to emulate modem port. In extensions manager I've disabled all that says "'modem", as I've been told anything that could try and use the internal modem could interfere with the Keyspan's sending data to the mini computer. There is no other modem. The problem is I haven't been able to send any data to the mini from the G4 thru the Keyspan. I open the initializing software on the G4, I turn the mini computer on, and it should immediately say "NOT READY". But it says nothing. There is no evidence that communication is traveling thru the Keyspan twin, it's attached serial cable, and into the mini computer. The divers for the Keyspan Twin seem to be loaded correctly on the G4. The wiring, and plugging alls looks correct. I even inspected the serial wiring inside the mini computer. Perhaps the Keyspan is bad... but the control panel does recognize it's existence. My knowledge of these things is poor, so I'm really stuck. Perhaps there is still something else trying to use a modem port, but what? Extensions manager has so many extensions. Any one? Thanks so much. Nick

Many of us are getting rusty with OS9 now, but hopefully we can help.

How were you using the digital back before its hard drive failed, I get the impression it wasn't as you are attempting with the G4. Was it fully fully functional then? Are you sure the Keyspan adapter is good, if you obtained it specifically for this job, did it come from a reliable source? Is Appletalk turned off and not switched to the Keyspan serial port?

Does the device appear in the Chooser, the communication utility under the apple menu in os 9

The chooser will also tell you if anything is using the modem port (if I remember it right)