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Scsi terminator 68 way active half pitch
SCSI II Half Pitch 68 Way Active Terminator
What is the difference between passive and active termination?
Passive termination is a resistor network, 330 ohms from ground to the signal line and 220 ohms from the signal line to termpower, which is an equivalent impedance of around 132 ohms. Since typical characteristic impedance of most cable is between 85 and 110 ohms, this is not a great match. The negation current varies with the term power voltage which can be from 4.0 to 5.25 volts, the pull up current would range from 16.5 to 24 mA. This would often required multiple steps to insure the voltage reached the 2.0 volt at the receiver. An active termination incorporates a small voltage regulator which generates a stable termination voltage from the raw Term Power (which may fluctuate) and allows the termination resistance to be lowered to 110 ohms, more closely matching the cable impedance. Active termination is recommended for all Single Ended buses at any speed, and is required for Single Ended Ultra SCSI speeds and above. New systems with active terminates may be powered from a 3.3 volt source, termpower can be from 2.7 to 5.25 volts.
