----- Original Message -----
Sent: Friday, September 15, 2000 3:07 PM
Subject: Re: Static Discharge
----- Original Message -----
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