DEC DECstation 5000 Model 100 Series Hardware Operator's Manual page 261

D
Setting SCSI ID Switches
If two or more drives have been given the same SCSI ID
numbers, you must reset the SCSI ID numbers on these drives,
so that each drive will have its own unique SCSI ID number.
Depending on the type of drive you are installing, different
methods may be required to set the SCSI ID switches that set
the SCSI ID numbers. Some drives use toggle switches to set
the SCSI ID numbers, and other drives use a system of pins
and jumpers, as shown in Figures D-1 through D-7.
To set the SCSI ID numbers on your drives, you may need
medium flat-blade and Phillips screwdrivers and small needle-
nose pliers.
Setting SCSI ID Switches D–1