Single-Ended, High-Voltage Differential, And Low-Voltage - HP SureStore 220mx User Manual

Operating This Jukebox on a SCSI Bus
A Brief Overview of SCSI
[1] Terminator - device required on each end of a SCSI bus to prevent reflected
signals
[2] SCSI Device - a device on the internal SCSI bus
[3] Host Bus Adapter - SCSI bus connecting point
[4] Host Internal - SCSI components internal to the host computer
[5] External - SCSI components external to the host computer
[6] SCSI Device - SCSI device external to the host computer
Single-ended, High-Voltage Differential, and
Low-Voltage Differential Interfaces
The SCSI bus is electrically implemented in three ways: single-ended,
high-voltage differential, and low-voltage differential. These terms come
from the way the signals are asserted on the bus.
Single-ended buses use a 5-volt signal that is referenced to ground. This
method makes the bus somewhat susceptible to noise and loss of signal
quality over distance. The maximum allowable length of a single-ended
SCSI bus was initially 6 meters (19.7 feet). Fast SCSI required the
maximum length of the bus to be reduced to 3 metres (9.8 feet).
High-voltage differential buses uses two lines for each signal and
Appendix B B-5