I read in another A+ book that there are 2 types of SCSI Adapters: Active & Passive. Could anyone in this forum please explain what's the difference between an Active & Passive SCSI Adapter?
SCSI Adapter Types
SCSI devices are typically daisy chained together to put all of the devices on the same bus (wire). Because the SCSI connection is a physical bus of devices that are networked together. It must also fall under the limitation of physical bus networks. There are two requirements that must occur for a SCSI bus to work:
- Every device must be *uniquely identified *
- Both physical ends of the bus have to be properly terminated
Failure of these can cause the SCSI bus to fail.
The proper termination can be active or passive:
- Passive termination is normally used on SCSI1 and SCSI2 buses. This is a simple passive resistor (OHMs) to stop "air noise" or signal reflection back on the cable .
- Active termination is used on the Fast-SCSI2 buses. This sees the signal on the wire and instead of using a simple resistor it see the signal and regardless of the ouput signal it can generate the matching resistance on the wire that will prevent reflection.
Hope this helps in your studies.
Edutainer Manager, ITProTV
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