AC Me wrote:
On Jul 14, 9:02 pm, "David Farber" wrote:
I moved into a new house and have new voip phone service via the
local cable 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

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

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?

Thanks for your reply.
--
David Farber
Los Osos, CA