While awaiting Verizon to turn on the service, and looking at filters,
splitters, etc., it dawned on me that I probably want to run the
unfiltered dsl line only into the surge suppressor. Since mine has
one input and two outputs, I then want to run one output to the dsl
modem and the other through a filter to the other PC, the dial up in
this PC, and the phone. Sound reasonable?
Now, if I eventually go for a "home run" direct from the NID to the
dsl modem, what do II use for a surge supressor in that case.
Your advice would be greatly appreciated.
I have heard reports of surge compressors causing problems for DSL.
If you are going to do it that way, it is reasonable.
I would put the surge supressor on the phone line (on the phone side
of the splitter), but leave the modem unprotected. That way you
avoid degrading the DSL signal. If the surge protector is any good,
it should absorb enough surge energy to give partial protection to
the modem. If you are unlucky, you lose a modem, but not your other
Note that there is already lightning protection in the NID (or there
should be). Check that the ground wire to the NID is intact.
First, if you think a plug-in protector is doing something
useful, then you read only what the manufacturer hopes you
read - which is not how surge protectors work. If you think
the protector will stop, block, or absorb surges, then it will
also block or absorb you DSL signal. Fortunately, that is not
what surge protectors do. Furthermore your phone line already
has an effective type protector, provided free by Verizon.
Second, protectors for telephone must be low capacitance
type. That made even more critical by DSL that operates in
higher radio wave frequencies. Again, the free and installed
Verizon protectors is low capacitance. The plug-in protector
may only further degrade the DSL signal as well as provide no
Third, the most common source of modem destructive
transients is AC electric - not the phone line.
How protectors for phone line operate was posted previously
comp.dcom.cabling entitled "problem between power and
communication cable" on 10 Feb 2005 at
Notice what defines effective protection. Not the
protector. Protection is defined by earth ground. The
protector is only as effective as its earth ground. That
Verizon 'whole house' protector is (should be if properly
installed) earthed to a single point ground.
Many thanks for the inputs. My son (the computer engineer)had also
said don't do it. I had the power to the house and panel upgraded a
couple of years ago and as part of that a new electrical ground was
set up according to whatever code governs it. Both the installers,
and the inspector said, now have Verizon and Cox both come out and
attach to the same ground point (to avoid "ground loops"?). They did.
I have had no problems re blown anything since.
Sounds like the earth ground was updated to post 1990
requirements. That causes one of the three incoming AC
electric wires to be sufficiently earthed. But the other two
incoming wires still are not earthed. Electricians know code
that is about human safety. Most have no appreciation of
transistor safety. Those other two AC electric wires also
must be earthed. But wires cannot be connected directly to
earth - and still provide utility power. So we install a
'whole house' protector in the breaker box. It is not
required for human safety but absolutely necessary for
transistor safety. Sufficiently sized and competitively
priced units are sold in both Home Depot and Lowes (and not in
other lesser quality stores such as Sears). The AC electric
'whole house' protector does same as the telco installed
protector in the NID.
That connection from each utility wire to a common earth
ground is secondary protection. Also inspect your primary
Most computer engineers really don't have electrical
training and are typically woefully ill informed about
effective computer protection. Best to let your son in on
these techniques necessary for minimally sufficient transistor
Does the system work? Well destructive surges occur
typically about once every eight years. Frequency varies with
geology and other local variations. Furthermore, if the
earthing and 'whole house' protectors are properly sized, then
you will never know that the system works.