Telephone wiring 101.
David Farber
company. The way it's configured is the cable from outside goes into the
modem, model number Arris TM502G, then the output of the modem, labeled Tel
1/2 goes into a telephone line splitter, then the single ended part of that
splitter, goes into a telephone wall jack which is supposed to feed the rest
of the house. The third connection of the splitter goes to my Uniden
portable phone system, model EXAI3428, which I will call system #1. It works
fine.
To avoid confusion with another Uniden system, a model EXAI5688-3, I'll call
that system #2. I want to hook up system #2 at a different wall jack in
another room. When I did, there was no dial tone. System #2 was working last
week in another home so I am fairly certain that it was ok. I have a
telephone line polarity checker probably better known as, "The Fox," made by
Triplett Corporation. The l.e.d. lights up when I plug it into the back of
the modem. When I remove the telephone line from system #1 and plug in the
Fox into the splitter, it doesn't light up. I disassembled the wall jack and
sure enough, if I hook up the red test lead to the green wire and vice-versa
for the green test lead, the l.e.d. lights up. Question 1, does it make
sense that system #1 can work if the polarity is reversed? I removed the Fox
and plugged system #2 in the same jack. System #2 didn't work. Then I
reversed the red and green wires in the wall jack and tried system #2 in the
wall jack in the other room. Still no dial tone. So I disassembled the wires
in that wall jack. The wires were so snug that I could only pull it out from
the wall about 1 inch. I looked behind the jack and saw that the phone wires
were the old style red, green, yellow, black wiring. When I reversed the
wires in the wall jack back in the room where system #1 was, I noticed the
wires were a white/blue pair. I then plugged the Fox into a jack in a third
room. The Fox lit up. I plugged in system #2 into the third room and got a
dial tone. Question #2, is there a way to get the red and green wires in the
wall jack that isn't working tied into the blue/white pair at the outside
box? And finally, why does the telephone line splitter reverse the polarity?
I tried another splitter and it did the same thing.
Thanks for your reply.
--
David Farber
Los Osos, CA
gree...@neo.rr.com
I don't think the splitter is really a splitter. My guess is it
isolates line 1 from line 2 so red/green from the cable modem goes to
one RJ11 and black/yellow goes to the other. You only have one line,
so only the first one works. Just plug a real splitter into the leg
that works. (These things aren't really splitters, but I'm using that
word because you did). Phones are connected in parallel.
AC Me
Hi David.
Polarity shouldn't matter, as far as I know. Many telephone leads have
the wires reversed. I discovered this many years ago when trying to
use off-the-shelf telephone leads for a 1-Wire cabling system. 1-Wire
needs 'straight-through' wiring while 'phones seem to work with either
straight-through or crossed. If you look at the 'phone leads that you
have on-hand (e.g. those leads that connect the 'phone to the wall
socket) I would be surprised if some of these were not crossed.
One other point to bear in mind is loading. Each device loads the
telephone network, if I might describe it as such. As far as I know a
standard telephone end-use system is designed to work with a load of
up to four units where a unit is a theoritical 'phone load. Any
individual telephonic device may have a load of several units. For
instance a particular 'phone (perhaps with fax an/or answering
machine) might provide a load of 2 units. The loads of all 'phone type
devices need to be added to get the total load. It is easy to forget
modems in PCs and the like. Just something to bear in mind should you
get your wiring sorted out.
Take care.
Mike
David Farber
Hi Mike,
As I pointed out, the polarity did matter because system #2 did not work
until I reversed the wires in the phone jack. Regarding the load on the
line, does a portable phone system which has its own power supply place the
same amount of load on the line as a stand-alone telephone?
gree...@neo.rr.com
Hi David,
I tried posting yesterday, but never saw my post. To answer your
recent question, only the designers know the load placed on the line
by a phone. However, they usually list it somewhere as the REN or
ringer equivalency number. 1.0 is the same as an old fashioned phone.
Newer phones are often less than 1.0. The ringer is the only thing
that matters when the phone is not being used to talk.
What I said yesterday that you may or may not have seen is the thing
you call a splitter is probably not a splitterat all. If the jack on
the modem allows for 2 lines, they probably use the middle two wires
for line one (often associated with red and green wires) and the outer
two wires for line two (often yellow and black). The "splitter" thing
connects the middle two wires from the jack to the middle two of one
output (line 1). It then connects the outer two wires to the middle
two of the other output (line 2). If you want multiple phones on one
line, only use the one output of the "splitter" thing. Get another
dual adapter to connect multiple phone to that one output.
Pat
Robbie Hatley
David Farber, regarding your phone wiring confusions, I have some comments.
Firstly, what is a "splitter"? That's not any kind of electronic component I've
ever heard of. Is is a multiplexer? A joint? A wire-pairs separater? Or
something else completely? Try checking it with an ohmmeter, or read the
manual if you have one, to find out what it really is.
Secondly, yes, polarities often get switched in phone wiring, sometimes
*several* times between the service entry and the telephone. (Obviously,
if the number of swaps is odd, the polarity will be wrong on other end.)
Thirdly, don't trust wire colors, those change too, sometimes *several*
times between the service entry and the telephone. (This, and the
polarity swapping, are because phone cables tend to be "dropped" from
the attic into the walls as separate snippets, and pasted together in the
attic. So a blue/white pair from the entry might become orange/white,
then green/white, then white/purple by the time it gets to your phone.
Fourthly, don't assume that because you get a dial tone, you have the
wire-pair you think you do. Call your own phone number. If it
rings, you do *not* have the right wire pair! You're illegally stealing
service from someone else instead. Instead, try other pairs until you
find the pair and polarity that not only gives a dial tone, but also gives
a BUSY SIGNAL when you dial your own number. That's your pair.
This is especially true in apartment buildings and businesses, but can
even be a problem in single-family homes, if multiple lines (some
possibly no longer in use) are installed.
Once I accidentally tapped into a pay phone that way at my apartment
building. Since the service entry is in the rear, and the pay phone is
out front, the installers ran the wires through my bedroom. Interestingly,
I was able to make phone calls without paying the $0.75 the pay phone
normally charges. I disconnected it immediately, though, both to stay out
of trouble, and because it wasn't the line my DSL was coming in on.
--
Cheers,
Robbie Hatley
lonewolf [[at]] well [[dot]] com
Wild_Bill
you) I've seen the blue/white pair used for a separate line in a single
household.
That would be Line 2, and Line 1 would be the common red/green pair.
Much of the newer phone hookup wire is 4 pairs, instead of the conventional,
decades old, 2 pair.
All of the lines should be connected inside of a network box (possibly
outside), but there may be other junctions between the wall jacks and the
network box.
There may be a jack and a pigtail cable to screw terminals, for each line in
the network box, at least that's the way they're made around here.
The other items, I'm unfamiliar with.
--
Cheers,
WB
.............
"David Farber" <farberbe...@aol.com> wrote in message
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