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My venerable self-installed Panasonic KX-T30810 has worked fine at home for almost 30 years. But recently one of the three CO lines won't generate a dial tone, regardless of which CO port on the KX-T it is plugged into. The other two CO lines work fine on all three KX-T ports.

I suspect that AT&T recently changed my physical copper pair, or what it is connected to in their CO. The killer is that the new line works fine with a modern touchtone phone, so of course the AT&T tech resolves my trouble report with "no trouble found" and says the problem is with my equipment.

When I use the KX-T to dial on the line without a dial tone, I get CO error messages like "Your call did not go through", or "It is not necessary to dial a 1 when dialing this number". If I just leave it off hook without dialing anything, it says "Your call did not go through" rather than the usual "If you'd like to make a call...". So the CO line is seeing something, but not liking what it sees.

I measure the on-hook voltage at the DMARC as 51.9V, and the off-hook voltage as 6.8V.

Any idea what's going on? Is there some modification I can make to the KX-T to make it compatible with the new CO line? Is there some way I can describe to the AT&T tech how the CO line needs to be different, or what's wrong with it?

Len, an engineer end-user

PS: Sorry for posting in "General", but I can't figure out how to post in the Panasonic forum.

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Did you check the cross connect or what ever you are using from the AT&T demark to CO port

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When I use the KX-T to dial on the line without a dial tone, I get CO error messages like "Your call did not go through", or "It is not necessary to dial a 1 when dialing this number". If I just leave it off hook without dialing anything, it says "Your call did not go through" rather than the usual "If you'd like to make a call...". So the CO line is seeing something, but not liking what it sees.

Obviously then the line IS going off hook. It sounds to me like either your system is seizing the line without your lifting a handset or there is something else on that line like an alarm dialer that is stuck off hook. Could also be bad wiring, a corroded jack, etc.

What happens when you call that line? Do you get a busy?

-Hal


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You said that it works fine with a touch tone phone. Where are you plugging in the touch tone phone?


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(Ah, I can reply now -- thanks, hitechcomm!)

- I don't think it's bad wiring, because when I swap lines at the DMARC, the problem moves to a different CO line on the KX-T.

- When I call the bad line from outside, it rings normally through the KX-T and I can answer it and talk on any of the eight KX-T7020 feature phones.

- The only other thing that I know was on the CO line was a "Whooz Calling" caller ID box, but I've removed it.

- When I test with a touch tone phone, I'm plugging the cable that normally plugs into the KX-T switch into the phone. So all the same house wiring is being used. (Of course it also works when I plug the phone directly into the DMARC.)

- The house wiring *is* the usual 50-year-old messy kludge, so maybe I'll try running a new clean test line from the DMARC to the KX-T and see if that changes anything.

Last edited by LenShustek; 09/21/20 02:44 PM.
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- When I test with a touch tone phone, I'm plugging the cable that normally plugs into the KX-T switch into the phone. So all the same house wiring is being used. (Of course it also works when I plug the phone directly into the DMARC.)

You say that you can move that line to other CO ports on your KSU and still have the problem? Or is it only on one port?

-Hal

Last edited by hbiss; 09/21/20 04:11 PM.

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The problem (no dial tone) happens on whichever of the CO ports on the KSU I plug that central office line into.

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Originally Posted by LenShustek
- The house wiring *is* the usual 50-year-old messy kludge, so maybe I'll try running a new clean test line from the DMARC to the KX-T and see if that changes anything.

Ok, I did that experiment, with a fresh pair directly from the "bad" line in the DMARC box to the CO inputs of the KX-T30810. On any of the three CO inputs, the behavior is the same: no dial tone on pickup, but calls are received ok. Plugging that fresh pair into a touchtone phone works fine.

The other CO lines in the DMARC work fine on all three CO inputs to the KX-T30810.

There's something about that CO line that is incompatible with the KSU, but that's not a complaint that AT&T will listen to since it works with a "regular" phone.

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Lenshustek

Your welcome.

There's something were missing here.
Let me think. (That's not easy)

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It needs to be asked Is the KSU set to tone dialing?


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