AGFA Horizon Ultra Scanner Owner's Manual page 45

The workstation does not start up.
Your workstation cannot find its hard disk due to a conflict with
the SCSI ID numbers of the devices you have attached.
Disconnect all SCSI devices (except the start-up disk) and
connect them one by one, beginning with the scanner, to
identify the device that causes the problem (switch all devices
off before breaking or making connections).
The scanner software cannot find the scanner
After opening the Scan dialog box, a message appears telling that
no scanner is connected, although the scanner is connected.
Check the Installation procedure, to see if you followed the
instructions. Pay special attention to the setting of the SCSI ID
number.
Maybe you did not wait long enough for all SCSI devices to
start up, before you switched your workstation on. Therefore,
try restarting your workstation. If this doesn't help,
Disconnect all SCSI devices and connect them one by one,
beginning with the scanner, to identify the device that causes
the problem.
The scanner reports errors during scanning (Apple Macintosh)
If this happens without error indications during the start-up
(see previous topics), contact your dealer or Agfa service
representative.
When starting up, the scanner makes a beeping noise and all the lights
are blinking.
This indicates a SCSI cabling problem. Be sure to immediately
shut down all machines in the chain and then solve the
problem. (Missing terminator? Bad cable? Internally
terminated component in chain?)
Appendix A — Troubleshooting 45