[SI-LIST] Re: E1/T1/E3/T3 requirements
- From: pwelling@xxxxxxxxxxxxxx
- To: si-list@xxxxxxxxxxxxx
- Date: Tue, 15 Jan 2002 11:34:12 -0700
Bob,
I think that you should plan to meet UL/IEC and FCC/CE-Mark (CE if you
actually have European requirements) in the design. Contract requirements
may exclude these specifications, but if a problem is traced to your design
and linked to an "up-time" issue due to AC crossover, lightning, other
system damage as a result of coupling to power subsystems, etc., it will be
your fault anyway. If not by company reputation, by personal reputation.
The same may be true of an emission problem or susceptibility problem.
It's not that hard to put these design recommendations in - unless there is
a problem already in the layout that you are fixing after release.
There have been ALOT of good comments on this subject and I'm sure that many
have learned much from the postings. Much of this isn't discussed in text
anywhere else or is difficult and time consuming to lays your hands on.
The SI LIST is working well as it spreads common design principles from
experienced engineers to others.
Thanks,
Philip Ross Wellington
Mgr. Signal Integrity & EMI
L-3 Communications CSW
-----Original Message-----
From: Bill Dempsey [mailto:BDempsey@xxxxxxxxxxxx]
Sent: Tuesday, January 15, 2002 9:37 AM
To: 'whizplayer@xxxxxxxxx'; Si-List (E-mail)
Subject: [SI-LIST] Re: E1/T1/E3/T3 requirements
Wow, I know this is an SI list but since we're
talking T1 on this thread I'll digress too...
I am astonished that you're in a central office
and yet you think you don't have to meet part 68
or UL. Cool. You state "since this is a digital
product".
In a previous private email I made mention of the
fact that if you're intraoffice, and *not* talking
to the outside world you're correct. Whenever you
connect to the outside, T1 has to meet the part 68
req's (i.e. lightning, AC crossover).
Just some thoughts. If you think you can get away
without doing it you're the first. Congrats.
Bill
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Bob Patel
Sent: Tuesday, January 15, 2002 9:32 AM
To: sandord@xxxxxxxxxxxxx; dmckean@xxxxxxxxxxxxxxx;
si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: E1/T1/E3/T3 requirements
Hi! Thanks for the inputs I have received so far. I
had a chat with our EMC engineer and he said that
there will be no lightning test done on this product
since this product will be at the Central office.Also
this is a digital product and UL1950, FCCpart68 does
not apply. I am just throwing out some reasons.
Thanks
Bob
Sandor Daranyi wrote: Doug,Somehow 12mil became
12mm along the way! :-)I got out of telecommunications
about 3 years ago and I don't have the rele=vant
standards handy but working from memory...What I was
referring to was that for example during a lightning
strike ther=e can be very high currents conducted
momentarily so even though I was s=aying overvoltage I
was really thinking about the resulting high
currents=which can damage the tracks. Wider PCB track
- more current.The "short to power line" was not a
reference to really high voltages just =something like
a short to 240Vac, 120Vac or something similar. I
guess t=he origin of that is (I'm guessing here) that
telecommunications cables m=ay get close to power
cables in real life and accidents can happen with
s=ome of these cables cut. The standards define
different levels of compli=ance and the operability of
the equipment during and after these tests, (=e.g.
data transmission errors under error condition but
equipment recover=s; operator intervention required to
restore functionality [like reset eq=uipment, change
fuse] etc.) but I digress.The "short to power line" is
probably not even relevant to the 12mil track =issue,
anyway. If that sort of voltage is present
transversally on the E=1/T1 lines than you'll need
tricks other than the 12mil line width and if=exactly
the same voltage is present on both tip and ring, than
you are O=K anyway, unless the overvoltage protection
circit is not correctly
desi=gned.Regards,Sandor---Sandor DaranyiSenior Design
EngineerArisctocrat Technologies Australia>
-----Original Message-----> From: Doug McKean
[mailto:dmckean@xxxxxxxxxxxxxxx]...> Depends upon what
the voltage levels being used in the=20> applicable
immunity and telephone standards for the
product.=20>=20> For air discharge breakdown, as a
"Rule of Thumb" I use =20> 1MV is 1 meter. 1KV is 1mm
or 40 mils.=20> And 8Kv is ... well ... 8mm. And 12KV
is, well, 12mm.=20>=20> Very rough estimates. Tip
geometry can greatly affect this.=20> All follows
Paschen actually for temp and pressure.=20> Telco
environs can be rough. Especially the Bellcore
standards. =20>=20> Hmmm ... 12KV sounds strangely
similar to an average street=20> level power line
voltage for a neighborhood which can run=20> anywhere
from as low as 2.4KV to as high as 24KV with the=20>
average about 12KV. Don't know. Just throwing out
some=20> ideas which come to mind. Someone
anticipating some=20> cross power condition like a
telephone line crossing with=20> a power line?
Interesting.=20>=20> For sensitive inputs, I've been
known to carefully calculate=20> the separations
required by the standards, then compare those=20>
separations needed to pass the levels of testing, then
multiply=20> the whole thing by 2 for a double safety
factor if I can get away=20> with it. But that's
me.=20>=20> Although 12mm sounds big, I'm not sure
what levels the surge=20> and lightning tests might
be. That would have to be checked.=20>=20> Personally,
the more separation you can give me, the better.=20>
Even if I don't need it.=20> -----Original
Message-----> From: Sandor Daranyi
[mailto:sandord@xxxxxxxxxxxxx]...>=20> Bob,>=20> If an
overvoltage protection stage is present (for
lightning=20> or short to power line) then it may make
sense to "beef up"=20> the tracks - at least between
the port connector and=20> protection device.>=20>
I've seen/done E1 designs with 12mil tracks at the
ports but=20> I've seen narrower (8mil) ones as well,
in other designs. =20> Take your pick...>=20> >
-----Original Message-----> > From: Bob Patel
[mailto:whizplayer@xxxxxxxxx]> > Sent: Tuesday, 15
January 2002 11:13> > To: si_list> > Subject:
[SI-LIST] E1/T1/E3/T3 requirements> >=20> >=20> > Hi!
In our previous T1/T3 designs we have used line widths
of=20> > 12mils for signals from the connector to the
magnetic i.e.=20> > line side of the transformer. I
asked why 12mil line width=20> > and my colleagues
mentioned that this is to meet immunity=20> >
requirements. I asked our EMC engineer and he did not
see a > > reason for 12mil line width. So, it would be
nice if somebody > > could shed light on this
requirement. > > Thanks a lot in advance. > > Bob > >
>
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