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 didn’t 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 doesn’t 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