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Re: [802.3af] Comment #172



Mike-

At 01:35 PM 1/23/2003 -0500, Mike_S_McCormack@xxxxxxxx wrote:

I had the poor taste to provide a comment asking that double insulated PDs
be allowed.  When this was discussed, I was asked to prepare specific
changes, in proper IEEE format, that would be required for implementation.
I've prepared the change pages and circulated them to some of you for
feedback.  I believe that they are now ready for prime time and would like
to provide them as my suggested remedy to my comment.  A PDF of the changes
is located at:

http://www.ieee802.org/3/af/public/jan03_2/mccormack_1_0103.pdf

Thanks

I support your changes in principle, some minor details here.
Regarding your change to 14 to read:
A MAU which has a PD attached to its MDI shall provide isolation between all external conductors, including frame ground, and all MDI leads including those not used by 10BASE-T.

A MAU that does not have a PD attached to its MDI shall provide isolation between the DTE Physical Layer circuits including frame ground and all MDI leads including those not used by 10BASE-T.

Change slightly (rephrase plus a couple of commas) to:
A MAU that incorporates a PD connection at the MDI shall provide isolation between all external conductors, including frame ground, and all MDI leads including those not used by 10BASE-T.

A MAU that does not incorporate a PD connection at the MDI shall provide isolation between the DTE Physical Layer circuits, including frame ground, and all MDI leads including those not used by 10BASE-T.

I assume (I didnít look as carefully) that the same would be true for Clause 40

BTW, What is the exclamation point for in 40.12.7 PME15a? It doesnít look like it belongs there.

What do you intend to do about modifying the text for 100BASE-TX?
        (Pasted here below)
You should read the whole thing because this text comes closer to dealing with our case than the vanilla cases in cl 14 & 40

From X3-263:1995 FDDI TP-PMD
8.4 Isolation requirements

LAN cable systems described in this standard are subject to at least four direct electrical safety hazards during their installation and use. These hazards are as follows:
1. Direct contact between LAN components and power, lighting, or communications circuits.
2. Static charge buildup on LAN cables and components.
3. High-energy transients coupled onto the LAN cable system.
4. Voltage potential differences between safety grounds to which various LAN components are connected.
Such electrical safety hazards shall be avoided or appropriately protected against for proper network installation and performance. In addition to provisions for proper handling of these conditions in an operational system, special measures shall be taken to ensure that the intended safety features are not negated during installation of a new network or during modification or maintenance of an existing network.

8.4.1 UTP isolation requirements

The UTP-PMD shall provide isolation between frame ground and all leads of the UTP-MIC, including those not used by the AOI and AII. This electrical separation shall withstand at least one of the following electrical strength tests.
1. 1500 V rms at 50 to 60 Hz for 60 s, applied as specified in subclause 5.3.2 of IEC 950:1991.
2. 2250 VDC for 60 s, applied as specified in subclause 5.3.2 of IEC 950:1991.
3. A sequence of ten 2400 V impulses of alternating polarity, applied at intervals of not less than 1 s. The shape of these impulses shall be 1,2/50 ms (1,2 ms virtual front time, 50 ms virtual time of half value), as defined in IEC 60.
There shall be no insulation breakdown , as defined in subclause 5.3.2 of IEC 950:1991, during the test. The resistance after the test shall be at least 2 MW, measured at 500 VDC.

8.4.2 STP isolation/coupling requirements

The STP cable plant consists of two distinct components, the twisted pair data path and the shielding system, which have different isolation/coupling requirements.

8.4.2.1 Data path isolation requirements

The 150 Ohm STP cable plant is consistent with the installed base of ISO 8802-5 Token Ring networks. As such, a voltage used for ring access control may exist in incomplete cabling systems. To protect against this, and other, hazards, the STP-PMD AOI and AII shall provide isolation which withstands the following electrical strength test.
1. 500 V rms for 60 s, applied as specified in subclause 5.3.2 of IEC 950:1991. 8.4.2.2 Shield coupling requirements
The STP cable plant relies on an equipotential bonded ground system to maintain system shield integrity. To ensure that excessive currents do not flow in the STP shield system, the potential difference across the shielding system shall be consistent with the applicable local safety codes.


Thanks for the good work on this.

Geoff