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Chevy
Guest
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 Posted:
Sat Jan 08, 2005 5:47 pm Post subject:
can an idsn surge protector be used with adsl? |
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i got a second hand isdn & AC protector. my telephone works fine
connected to it but my pc doesnt connect when i try with adsl.
is there any difference between adsl and isdn signals which could be
related to this problem?does the protector need its own inline filter?
thanks
c |
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Ari Wuolle
Guest
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| Posted:
Sun Jan 09, 2005 3:18 pm Post subject:
Re: can an idsn surge protector be used with adsl? |
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ChevyChasen@yahoo.com (Chevy) writes:
| Quote: | is there any difference between adsl and isdn signals which could be
related to this problem?
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Yes, ADSL signals use higher frequencies than ISDN. If your protector
is not designed with ADSL in mind, it may very well filter out the
ADSL. Some protectors on the other hand won't mess with ADSL, so it is
something that just has to be tried out.
In your case it is quite clear - if the ADSL won't work when the
protector is in place, it is not suitable for ADSL. For trying out
other protectors, it is best to check your ADSL router/bridge's
diagnostic. Check the line attenuation and signal to noise ratio with
and without the protector. If attenuation dramatically increases with
the protector in place, the protector is not suitable for ADSL.
Also, if signal to noise ratio is better than 6 db without protector
and worse than 6 db with the protector, it is best to find a better
protector. If your line is very long and you are nearby 6 db noise
ratio even without a protector, it may be that any extra attenuation
on the line is too much. In that case you cannot might not be able to
use any protector on that line.
| Quote: | does the protector need its own inline filter?
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Before the protector? No. Filters block ADSL signals and if you put a
filter before the protector, your ADSL is certainly not going to work
behind the filter and protector.
Filters are only used to keep POTS devices (phones, faxes, burglar
alarms, clid boxes) messing up with the ADSL signals and also to stop
ADSL signals being picked up by your phones, which may turn them into
a nasty background hiss.
Ari Wuolle |
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w_tom
Guest
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| Posted:
Sun Jan 09, 2005 10:41 pm Post subject:
Re: can an idsn surge protector be used with adsl? |
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How is a filter going to know the difference between ADSL
radio frequencies and lightning radio frequencies? It is
not. Either it degrades both - or it does nothing. But then
filters do not even claim to provide transient protection.
How does an in-line protector stop surges if it does not
filter surges? Bottom line: it claims protection from a type
of surge that typically does not exist. It provides no
effective protection.
Learn why your telco, with overhead wires everywhere in
town, need not shutdown POTS, ISDN, and ADSL service during
every thunderstorm. That's $milllions in equipment at risk.
They use simple protection. They connect every incoming wire
to earth ground via a surge protector. A protector best
located 50 meters away from equipment AND directly to at
single point earth ground. Not just any earth ground. The
single point ground. Every incoming wire connects to this
same ground. An effective protector connects each wire, short
distance, to earth ground during a transient.
Filter does not provide transient protection for the telco.
Why would an in-line protector do any better? Expensive telco
equipment must not be damaged by any direct strike. You
require same. A protector that costs less money is made
effective by adjacent earth ground.
Chevy wrote:
| Quote: | i got a second hand isdn & AC protector. my telephone works fine
connected to it but my pc doesnt connect when i try with adsl.
is there any difference between adsl and isdn signals which could be
related to this problem?does the protector need its own inline filter? |
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Guest
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James T. White
Guest
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| Posted:
Sun Jan 23, 2005 1:58 pm Post subject:
Re: can an idsn surge protector be used with adsl? |
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<ChevyChasen@yahoo.com> wrote in message
news:1106413892.287877.12170@c13g2000cwb.googlegroups.com...
things are indeed capacitors and the yellow things are metal oxide varistors.
The capacitors don't really clamp the voltage, they just limit the rate at which
it can change. The varistors do the clamping. The caps and MOVs are on the AC
side. There is also a neon light and current limiting resistor which serves as
a power on indicator.
The rest of the circuit is what protects your ISDN line. The green things are
three terminal gas tubes. The horizontal black things (labeled D1-8) are
diodes. The vertical black things (labeled TVS1-2) are either zener diodes or
something similar. Presumably, the red and black wires are one pair and the
green and yellow wires are the second pair. The zener diodes are probably rated
at somethign like 15v limit the voltage across the wires in each pair. The
diodes are there to route the more positive wire of each pair to the cathode of
the zener. As zeners are typically significantly more expensive than simple
diodes, this allowed the manufacturer to save some money by using only 2 zeners
instead of 4. The gas tubes limit the voltage between the pairs and provide a
path to ground. Most of the gas tubes I've seen fire at 75 V or higher across
any two terminals. When they fire, all three terminals are effectively clamped
together. Gas tubes can handle a lot of current (tens or hundreds of amps) with
out being damaged but fire in tens of microseconds while zener diodes can only
handle something less than ten amps but begin conducting in nanoseconds. Some
folks call this a "staged protector" since the zeners begin clamping first as
the voltage rises above their rating and then the gas tubes fire if the voltage
continues to rise. In the case of your protector, since the input and output
are directly in parallel with both the input and output jacks so there is a good
chance that the zeners may be "cooked" by a large surge by the time the gas
tubes fire. As zeners almost always fail shorted, the ISDN circuit may not work
but would still be protected until you replace the protector.
Hope this helped.
--
James T. White |
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