atcomsystems.ca/forum Forums Other TDM Phone Systems 1A2 and Comkey Telephones & Systems real interesting service call

Here's something I'm still stumped on and need someone to enlighten me and my installers. About a week ago, I had a few jacks terminated at my house after the electrician ran a few new CAT-5 cables in addition to some 23-pair cables for my 1A2 system to be installed someday. (Yeah, I know I could have terminated them myself and saved a bundle, but I didn't have the time and worried I might cut off a wire too short.) Anyway, everything worked fine until last night when I couldn't dial out with my polarity guarded TT phones. And it was the whole house. My thought: the phone co. must have reversed the wires because they all were working, all 17 of them. I asked the installers to come back and modify a jack in our bathroom and reverse the wires. They did at the network interface but the phones still couldn't dial out and showed the polarity was still wrong. I told the installer he must have confused the 2 wires and reverse them again. Same thing again. And wires from phoneco are correct. Well, if switching them outside doesn't work, switch them in the basement. That worked. But how or why?
Wiring goes through DSL filter which is not new and a Viking Ring Booster which was added last week. Any thoughts, guys?

The answer sounded simple until I got down to your last few sentences. I'm stumped as well.

Who's your dial tone provider?

So polarity wouldn't be the issue.

Are you saying that these are phones that have built-in polarity guard circuitry, or are they phones to which you have added the PG?

Maybe the phone co installer was confused. He may have understood you to mean that he needed to reverse the wires on BOTH sides of the NID connections. That would essentially negate any reversals. Did you actually watch him do the reversals, or did he just say he did them, and you believed him? I'm not saying he lied to you, just that he may not have understood what he needed to do.

Then, when you did the reversal yourself in the basement, you fixed the problem.

is it only the phones with the polarity guard that aren't working ?

can a plain old cheapo phone call out ?

have you tried the polarity guarded phone plugged in at the NID ?

if you dont feel competent enough to swap polarity at the NID or take a jack of the wall and swap the wires how do you feel competent to install a polarity guard ?

He said he fixed it already by reversing the wires in the basement.

1. Perhaps I used incorrect terminology with polarity guarded. These are old-style 2500 TT telephones that require correct tip and ring to dial out on.
2. My provider is good ole AT&T Indiana.
3. I did not install a polarity guard so I am sorry if I gave anyone that impression. But it is not a matter of competence with me - it is a matter of time and dealing with wiring that has no "give." It comes out of the wall a fixed length - no slack. That is the way the electrician pulled the wire.
4. I saw the installer physically change the two wires in the NID. Today I went out and confirmed he was working on line 1 as we have 2 lines coming into the NID.
5. Yes, I could dial out on a rotary phone or phone without polarity issues.

6. yes, I used a polarity tester (Radio shack) at the NID and the POTS line was correct polarity. Had no trouble dialing out via NID so problem obviously house wiring.

By definition (and common usage of the language) a phone with a polarity guard "guards" against wrong polarity. There would be no reason to "guard" against correct polarity.

So, older phones, made during the period when the phone company charged extra for DTMF service, did not guard against reversed polarity, for a financial reason. TPC could (and did) reverse line polarity at the MDF when they discovered a subscriber "illegally" using tones to dial out.

Later, when DTMF service became "free" there was no reason to prevent dialing. In addition, with the advent of end-to-end signaling, phones with polarity guards were needed to prevent blocked dialing after call completion that might involve inadvertent polarity reversals.

We're glad you got it straightened out. I would not trust any tester made by RS, though. The best tester is the phone itself. An experienced repairman can pretty much tell wazzup just by listening to the sub's phone.

Is the correct phone parlance perhaps "polarity sensitive"? Thanks for explaining the difference to me about polarity guards and why the phone company had the financial interest to not use them.

Even though everything is working, I still can't understand why switching the two wires at the NID did not affect the polarity inside the house. And I saw the installer physically do it.