SCSI Terminators

Two terminators are needed to terminate a SCSI chain, one at each end. SCSI adapter cards have built-in terminators leaving the last peripheral on the chain to be terminated. For non-Differential SCSI which covers the majority of cases, the following are recommended:

• Use Passive SCSI terminator if total chain distance is less than 6ft, and I/O speed is 10Mbps or less. Passive terminator sits on the bus to minimize reflections at the end of the cable and simply provides an impedance that’s close to the impedance of the cable.



• Use Active SCSI terminator if SCSI II and III devices are used, and total length of the chain is 20ft or less. Active SCSI terminator prevents signal reflections to provide data integrity and works to control the impedance at the end of the bus by using a voltage regulator, not just the power supplied by the SCSI controller. It is more reliable than passive termination for high speed devices and long distance applications.



• Use Forced Perfect Terminator (FPT) if total distance is more than 20ft, more than 5 devices are chained, and when passive or active terminators cannot do the job. FPT terminator goes beyond stabilizing the power applied to the terminator by altering its impedance to actively compensate for variations among many different cables and devices by means of diode switching and biasing. It has built-in troubleshooting LEDs.



• Use Differential Terminator only for SCSI systems that uses the Differential SCSI bus, also known as High Voltage Differential (HVD). Use Low Voltage Differential (LVD) Terminator for Ultra2, Ultra160, & Ultra320 Drives
  

Cen50M Ext.

HPDB50M Ext.

HPDB68M Ext.

HPDB68F Int.

HPDB68M/F Int.

IDC50M Int.

IDC50M/F Int.