Apple 627, 1230 user manual About SCSI termination, Factory setting

For example, the internal hard disk drive is, by convention, always assigned SCSI ID 0 (internal). The system software shows the hard disk at that location.

You can connect a total of seven internal and external SCSI devices to the Macintosh. Each device must have its own unique SCSI ID number, from 0 to 6 (or from 1 to 6 if you have an internal hard disk drive installed).

About ID numbers: Do not assign numbers 0 or 7 to the scanner. The default setting for the internal hard disk drive is 0, and for the computer, 7. Make sure you use a number that is not assigned to any other SCSI device because each ID number must be unique.

Factory setting

The SCSI ID number for the Apple Color OneScanner is set in the factory at 2, with termination on (see the next section), but you can change the setting if necessary.

About SCSI termination

To ensure accurate transmission of information, a terminator is used at the end of a SCSI chain, even if there is only one device in the chain.

Any Macintosh computer with an internal hard disk drive contains its own terminator. This means that you need only one other terminator (internal or external) attached to the last device in the chain.

The Apple Color OneScanner has an internal (built-in) terminator. This control switch can be set to various SCSI ID numbers. Each number can be set with termination on or off.

mWith termination on, information stops at the scanner.

mWith termination off, information can pass through the scanner and travel onward down a chain to another SCSI device.

160 Appendix C