Thread Links Date Links
Thread Prev Thread Next Thread Index Date Prev Date Next Date Index

RE: Selection Criteria for choosing a Discovery Method

Title: RE: Selection Criteria for choosing a Discovery Method

In general, I agree with your proposal list, and I state my responses below.

(I-2) Minimizes cross-talk interference potential to Gigabit Ethernet and
unidentified future services

I think that the "future" part is kind of nebulous. We should state the requirements that exist now.

Also, I'd rather say does not interfere with 1000BASE-T, rather than minimize.
Otherwise, you could argue that a DC scheme will always minimize interference compared with an AC
scheme. And you would be right.

(I-3) Minimizes EMI

Clearly, only a true "DC" discovery scheme can do this.
Are we then done?

(R-1) Avoids "false positive" detections (quiet and noisy environments)
(R-2) Reliably delivers power to proper PEs (quiet and noisy environments)

We need to define "noisy" environment.
How about passing the EFT (electrical fast transient) test and radiated immunity at 5 volts per meter.
Also, we should use the Campbell clamp fixture to determine where the discovery process fails vs frequency,
as it is stimulated with common mode fields.

Maybe we should add these cables to test: CAT-3, CAT-5, and CAT-6.

(R-3) Avoids giving power to paralleled devices

We need further definition on this one.
No discovery method proposed so far can detect a short paralleled legacy device, depending on it's input configuration.

Also, I would add to the list:
"Avoids failure to detect a valid powerable device".
"Automatic recovery from a cable discharge or ESD event".

(D-1) Low risk of equipment damage IF power is ever inappropriately

How is this an issue of the discovery method, that is not covered above under robustness?

(C-1) Leverages the necessary function of precisely monitoring current
levels to inexpensively perform detection

Doesn't this assume a fact that is not yet in evidence?
Are you saying that discovery and load current measurement must use the same method?
To repeat: Are we then done?

Other survivability tests:
Ability to survive RJ-45 Hipot test, whether DTE power is on or off, and meet the leakage resistance at the end of the test.

- Rick