A Fable

The Good Output was known by all in the eDART kingdom to be a fully trustworthy and reliable fellow. He spoke to the robot and would only tell him when a part was good. So the robot never needed to guess. Besides, he only listened to what the Alarm Settings told him and would only say “Good” to the robot when told. Alarm Settings was a very smart guy. He knew every important sensor, listened to each one and made careful judgments about the parts.

But the king decided not to hire the Good Output, being that Good was a little more expensive than Reject. Also the king did not like his philosophy. Instead he hired the straight talking Reject Output because that is what his robot liked to hear anyway. It was easy for the kings men to get the robot and Reject to talk to each other.

One day a sensor got lost. No one knows how. He just stopped communicating (I think his cable was unplugged; happens to us all). Alarm Settings noticed it and marked him “Suspect”. With the sensor silent he didn’t know what was going on, whether the parts were good or bad. Alarm Settings told the Reject Output that he did not know the answer any more. But Reject said “That’s ok. At least you are not telling me they are rejects.” So he never turned his output on. He’s not a bad chap. Just a little limited.

Sadly, a bad part was made that was not full. But no one knew about it. Alarm Settings was still unsure and so could not tell Reject that there was a reject. So Reject did not tell the robot to reject that part and an evil part escaped into the world. As far as we know that part is still at large and the king sits with trepidation waiting for news of the mischief the bad part might do.

So the king fired Reject and hired Good instead. After that Good would only let the robot keep the parts if all the sensors were alive and well. But it was a sad and costly mistake.

Moral:

Always use the Sorting Output / Good Control signal if you want to be sure no un-measured parts escape (tip #1)

If your equipment will not accept a “Good” signal then use the Sorting Output / Good Control anyway and wire the equipment to the “Normally Closed” contact (tip #2). You only need Sorting Output / Reject Control for 3-way sorting.