Apple Macintosh PowerBook 145B - Manual (Page 239)

Checking that the SCSI chain is properly terminated
To ensure accurate transmission of information, a chain of SCSI
devices must have a terminator at each end. Terminators are built
into some SCSI devices and can also be added externally.
m Your PowerBook’s internal hard disk, which is always the first
device in the chain, has a small built-in terminator. However,
for reliable information transfer in a chain of SCSI devices, it
should be supplemented with an external terminator as
described in these instructions.
m External SCSI devices from Apple do not have built-in
terminators.
m External SCSI devices from other vendors may have built-in
terminators; see the documentation that came with the
device.
If you are attaching one SCSI device
Make sure that there is
m an external terminator between the HDI-30 system cable and
the SCSI device and
m an internal terminator in the SCSI device, or an external
terminator attached to the device.
If you are attaching more than one SCSI device
Make sure that there is
m an internal terminator in the first external device, or an
external terminator between the HDI-30 system cable and the
first device;
m an internal terminator in or an external terminator attached to
the last device; and
m no other terminator (internal or external) in the chain.
If you have too many devices with internal terminators, your
authorized Apple service provider can remove extra terminators.
Correct chain configurations are shown in the illustration on the
following page.
SCSI terminator
226 Chapter 13: Expanding Your Computer System