Agreed. If twisted to at least Cat3, running along side a long run of romex
(for example) for the ENTIRE length of even the largest residence (rare)
presents no degradation of signal. Separation is always best but not always
Others will tell you different, but I have ran phone, cat5e and Romex all
together. In fact, when I wired my garage, the phone cable (I used cat5e
cable) was ziptied to the main run of Romex cables for the whole garage. No
problems with it at all. My phone cable is brought to my house hanging
underneath the main lines, and people want you to believe that a 120V cable
is going to cause a interference problem. nada!
It would if you were using the old four wire, non twisted cat 0 phone
wire. Since you are using cat 5 wire which is twisted pair the twist
cancels out the common mode interference that would most certainly have
been picked up with the old untwisted wire.
As for the drop to the house which is likely non twisted drop cable, it
is not in close enough proximity to be a problem. The magnetic field
that induces interference drops off in strength rapidly with distance.
I realize the original post was about phone wire, but I'd be interested
to see a data analyzer hooked up to some cat 5 data cables that were
run next to electrical wires. I'd be curious as to how many dropped
packets and retransmissions due to errors would occur. The average
user might not ever notice a problem but errors like these increase
network traffic and would drive a network engineer up a wall.
Pete C. wrote:
At 100mz I say ZERO. I have not tried the 1gz LAN. I did a lot of
testing with Ethernet and Token Ring cables in my old office. I was
not able to reproduce any of the urban legend "interferance" with
flourecent light ballasts, mixing phone and data or paralleling 60hz
This was using the IBM LAN sniffer program and the normal office
traffic on the LAN along with me shipping big files around.
Agreed, but I think your concern is EXACTLY WHY Cat5e was developed.
I suspect that, except in isolated cases, electromagnetic interference with
Cat5e is virtually non-existent. I'd bet that you'd find more drops and
retries due to poor connections such as at routers, patch panels, and
improperly made/crimped RJ45 ends, to name a few likely spots. Just a
The twist rate is actually a littler different for each pair in that
that is true. It is best to not disturb the twist until you are ready
to make the punch andf then only as much as necessary.
At slower data rates ir will probably never affect you but as we start
getting up around a ghz on copper it is the difference between working
It wasn't that long ago that people were saying 100mz would be the end
of the line for twisted pair.
Not sure about the interference, but you're right about not meeting
code. The NEC, in Sec. 800.133, specifies a 2 inch separation between
"communication cables" and power cables unless the cables are somehow
physically separated, such as by a conduit.
On Fri, 24 Nov 2006 23:32:51 -0600, firstname.lastname@example.org ()
Remember that if the is no current on the AC lines, there will be no
magnetic induced fields, even though the lines may be energized.
Since the dawn of telephone communication, crosstalk between the phone
lines (and from external sources) has always been a problem, although,
now it has been minimized due to a better understanding, and improved
materials and installation techniques resulting from scientific
The first phone lines were single conductors with a common ground like
telegraph lines and suffered from severe crosstalk and power line
interference. Multiconductor circuits, loading coils, and twisting of
conductors helped to solve the problems. Ultimately, phone lines and
switches became digital (ESS) long before the Internet became
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.