Robert,
The reason for the discharge path is the IP Phone which may have only
a LAN connection.
In the telephony domain, one purpose of the discharge path is to slowly
discharge a user that contacts the phone.
When I did a rotational assignment at Indianapolis in the mid 60's,
they had an interesting story concerning the first colored phone.
The color plastic unlike the black plastic was an excellent insulator.
Due to the cost premium, users were executive with carpeted offices.
These users often had accumulated a large charge which was discharged when
the user talked into the transmitter in the hand set. Black phone
users were discharged by the poor insulating plastic.
Dieter
RDLove wrote:
OK,
we got email notes from two of the experts (Larry and Roger) indicating
this is not a real issue. Unless there is strong objection, I will
take it off the issues list. If there is strong disagreement (and
this process will be in effect for any potential issues raised) then it
will stay on the list until the task force resolves it. Best
regards, Robert D. Love
President, LAN Connect Consultants
7105 Leveret Circle
Raleigh, NC 27615
Phone: 919 848-6773
Fax: 720 222-0900
email: rdlove@xxxxxxxx
----- Original Message -----
Sent: Friday, September 15, 2000 4:21
PM
Subject: RE: Static Discharge
I wasn't raising
an issue, Bob.
Dieter was just
asking how Ethernet avoided the Telco grounding, and I was explaining "what
it is". At least, that's what I intended.
Roger seemed
to think I was taking a position of some sort. Look at Dieter's post, then
mine.
Cheers,
Larry
-----Original Message-----
From:
RDLove [SMTP:rdlove@xxxxxxxxx]
Sent:
Friday, September 15, 2000 12:09 PM
To:
802.3af
Subject:
Fw: Static Discharge
I meant to send the attached to all
802.3af. Sorry for the duplicate email to you, Larry.
Best regards,
Robert D. Love
President, LAN Connect Consultants
7105 Leveret Circle
Raleigh, NC 27615
Phone: 919 848-6773
Fax: 720 222-0900
email: rdlove@xxxxxxxx
<mailto:rdlove@xxxxxxxx>
----- Original Message -----
From: RDLove
<mailto:rdlove@xxxxxxxxx>
To: Larry
Miller <mailto:ldmiller@xxxxxxxxxxxxxxxxxx>
Sent: Friday, September 15, 2000 3:07 PM
Subject: Re: Static Discharge
Larry, thanks for your input.
I agree with all you say, but still don't know if this is an issue that
needs to be addressed. I would like to hear from other experts on
it.
Best regards,
Robert D. Love
President, LAN Connect Consultants
7105 Leveret Circle
Raleigh, NC 27615
Phone: 919 848-6773
Fax: 720 222-0900
email: rdlove@xxxxxxxx
<mailto:rdlove@xxxxxxxx>
----- Original Message -----
From: Larry
Miller <mailto:ldmiller@xxxxxxxxxxxxxxxxxx>
To: Dieter
Knollman <mailto:djhk@xxxxxxxxxx>
; stds-802-3-pwrviamdi@xxxxxxxx
<mailto:stds-802-3-pwrviamdi@xxxxxxxx>
Sent: Friday, September 15, 2000 1:07 PM
Subject: RE: Static Discharge
Ethernet stuff
is not intended to run outdoors like regular telephones. The biggest risk
these days is picking up static electricity when the cables are pulled
through conduits and wiring troughs. That seems to get worse the better
the cabling gets (cat5E and up) due to triboelectricity.
The insulation
scheme was chosen to accommodate ground level shifts within building premises
wiring (different AC feeds to different boxes). The wiring cables float
(up to 2250 VDC) with respect to ALL of these. There has been much discussion
in the 802.3af work group on how to handle DC-powered cables. The 802.3
standard defines two environments ("A" and "B") with respect to port-to-port
isolation (See 802.3 spec or some of the 802.3af presentations on the IEEE
public site).
You are supposed
to used fiber optic links if you exit a building. IP phones are supposed
to be within a building, with the only wiring going to an Ethernet hub.
Wall warts if used are double insulated.
The 2kV caps
are not supposed to be leaky.
Larry Miller
-----Original
Message-----
From: Dieter
Knollman [SMTP:djhk@xxxxxxxxxx]
Sent: Friday,
September 15, 2000 9:53 AM
To:
stds-802-3-pwrviamdi@xxxxxxxx
Subject:
Static Discharge
Hi,
My
background is telephony. I'm totally new to 802.3, so please excuse
my ignorance.
One thing that appears strange is
the lack of an intentional discharge
path for the potential on the cable.
The only means that I have found is
breakdown of the common mode
termination capacitors.
Are these caps with 2 kV rating intended
to be leaky?
On
POTS line interfaces the Tip lead is typically biased around ground
and serves as a discharge path to
earth ground for Analog Sets. Do the
IP Phones require a discharge path
via the LAN?
Dieter
Knollman
DMTS
Lucent
djhk@xxxxxxxxxx
|