Apple ColorLaserWriter 12/600PS - Manual (Page 163)

IMPORTANT The external hard disk you connect to the Color LaserWriter
12/600 PS printer must supply 5 volts DC to the SCSI bus to work properly.
Check the documentation that came with the hard disk for information about
SCSI voltage.
The kind of SCSI cable terminator to use with disks connected to the printer
can be black or gray. To purchase terminators, contact an Apple-authorized
dealer.
Before you connect your external hard disks, make sure that each one has a
unique SCSI ID number. Do not turn on or attempt to use the printer or any
attached hard disk until each disk has been assigned its own number. Do not
use SCSI ID #7; it is reserved for the printer’s CPU. SCSI ID #0 is used by an
internal hard drive, if one is installed.
Setting the SCSI ID number
Each SCSI device attached to the printer must have a unique ID number.
You assign a SCSI ID number by setting the SCSI ID switch on the back
panel of the disk. Follow these steps.
1 Make sure the hard disk and printer are turned off.
2 Set the SCSI ID according to the hard disk manufacturer’s specifications.
IMPORTANT Before you turn on the printer, be sure to turn on any external
hard disks attached. If you turn on the printer first, it may not recognize some
attached external hard disks. When this happens, the printer may not start up
properly, and you won’t be able to print anything. To fix this problem, make
sure all the hard disks are turned on, then restart the printer.
138 Chapter 5