Apple SCSI Terminator: Description of Active Terminator

This article provides a description and information for the new Apple Active SCSI Terminator part number M3503LL/A.
This article has been archived and is no longer updated by Apple.
The Apple SCSI Active Terminator is the new style of SCSI terminator (service part number 922-1185). It replaces service part number 658-8032.

Question: What does it do?
Answer: The Apple SCSI Active Terminator includes a voltage regulator and capacitors to filter the term power. Active termination is one of the alternatives specified in the new SCSI specifications. The active termination is much less sensitive to variations in the termination power supplied by various SCSI devices.

The active terminator functions as follows:

The terminator voltage supplied by the device, typically between 4.25 Vdc and 5.25 Vdc is applied to a low drop voltage regulator and the output is regulated to 2.85 Vdc which is then applied to 110 ohm series termination resistors.

Question: Does it turn off or turn on?
Answer: No, the regulator is on when ever termination power is supplied to it.

Question: Why isn't there a LED on it indicating activity?
Answer: A complete redesign of the tooling for the terminator housing would be required to fit an LED to the terminator. Since the terminator is at the back of the peripheral, out of sight of the user, the benefit of an LED would be minimal.

Question: Does it adjust for resistance or impedance issues?
Answer: No, its designed for regulating the termination power supplied by SCSI devices.

Question: Why would someone want this one over the old one?
Answer: Improved reliability of the term power signal level.

Question: Did the finished goods part number change to a /B?
Answer: No, this is the first revision of this part, not a revision of the old part. The new part number is M3503LL/A.

Question: How can I differentiate it from the old terminator from the outside?
Answer: The previous non active SCSI terminator has part number 590-0304-A embossed in the plastics. The new active SCSI terminator has part number 590-0772-A embossed in the plastics.

Question: Is it required by any current or future computers?
Answer: This new active SCSI terminator is not required for any specific computer or peripheral from Apple. It is a replacement for the current terminator. The IIfx and some LaserWriter printers still require the black terminator.
Published Date: Feb 20, 2012