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Interesting call. No ringing voltage
#636040 03/24/20 12:15 AM
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ChrisRR Offline OP
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Got a call Friday from a friend, his phone wasn't ringing. Outgoing calls were/are working fine. Ran some quick checks Friday when I went out, but I couldn't get into his apartment building's telephone closet, so I did the best I could from the Interface Jack in his apartment. Seemed to me like the ringing voltage was being shunted somewhere. My first thought was maybe a faulty protector. Today I was able to go back out and get access to the closet. I quickly found his pair, lifted the jumper from the BET to the 66 blocks, and tested right at the block in the terminal. Same story. No ringing voltage. DT was fine, calls out just fine, if I called the number from my cell phone, I could hear where the ringing should have been, if that makes any sense. The line would get super quiet, like it was being shorted somewhere. Everything else seemed normal. I could pick up the line and answer it, I heard the caller ID burst after the first "silence", even his phone in the apartment would show the caller ID when I tried calling it on Friday. I swapped out the protector with multiple others, it's a 100 pair BET and there's only about 4 active pairs on it, and dozens of pairs that aren't jumpered off to anything, so I wasn't worried about putting someone out of service.

Obviously at this point, the trouble is either in the outside plant or even in the CO, but it has me curious. A tech is supposed to be dispatched tomorrow, and I'll try to be there, but does anyone have any thoughts on what this problem might be?

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Re: Interesting call. No ringing voltage
ChrisRR #636044 03/24/20 04:52 AM
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This is a very common issue on POTS lines. Pair gain, or remote terminal (RT) equipment (Pairgain, Adtran, SLC96) provides remote shelves of line circuits from the CO that are fed by fiber or multiple T-1 spans to a geographical area, such as a city block or sub division. These shelves have local ring generators that fail, and fail often. Your customer is probably one of 4 working POTS lines working on that shelf, so the telco hasn't received any complaints. You're hearing the ring battery being sent from the CO to the RT, but it isn't being duplicated to the premises.

NOW, getting the telco to admit to this when calling for repair is another subject. They'll swear that everything is leaving the CO just fine, and it probably is. Your best bet is to report the trouble via the telco's on-line trouble reporting portal and make the comments stated above. Hopefully, a CO technician will pick up the ticket and understand what you're saying.


Ed Vaughn, MBSWWYPBX
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Re: Interesting call. No ringing voltage
ChrisRR #636050 03/24/20 04:26 PM
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I am with Ed on this one. If they find the CO issue and fix it we usually get the canned nothing wrong here...musta been something at customer site.


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Re: Interesting call. No ringing voltage
EV607797 #636053 03/24/20 05:51 PM
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Originally Posted by EV607797
...Your customer is probably one of 4 working POTS lines working on that shelf, so the telco hasn't received any complaints...

A year or so ago a client's rural radio transmitter site POTS line became grounded again. The local supervisor (small co-op telco) said we were the last copper customer on the DMS10 switch in the neighboring town, and would you like us to trench a fiber into your site on their dime. Sure! smile

Last edited by grich; 03/24/20 05:51 PM.
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Re: Interesting call. No ringing voltage
ChrisRR #636126 03/27/20 08:10 PM
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ChrisRR Offline OP
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So to provide an update...

First and foremost, the issue is fixed. Consolidated owned right up to it being a problem with their equipment. They went out the next day and fixed it.

That being said, I didn't want to go poking around other customers lines, but I did check the line for the elevator phone in the building, and it rang just fine. (Different channel bank, perhaps?) A few other people in the building who do still have POTS lines told us they were working fine.

When I called repair, they put me on hold while they "checked the line from their end". I figured this was some BS, but the lady actually came back and said they saw a problem on the line. I wasn't there when the tech came out, but the customer said "The guy said it was something underground" Whatever that means, I guess. I didn't think they put electronics below grade, I thought they'd be in a hut or a cabinet of some kind.

Either way, problem is solved. The phone rings again. I was mostly curious for my own learning purposes.

Thank you guys.

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Re: Interesting call. No ringing voltage
ChrisRR #636127 03/27/20 11:40 PM
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It might have been a ring trip short (like 80k-200k ohm) on the pair. It's high enough resistance to talk and make calls on, but if the CO runs across it, it shorts out and the ring cant get through. An ac voltmeter with good response might have seen small or 0 volts across the pair when ringing, and 50v to ground when ringing.

Usually this also causes the CO to think the call was answered and tries to complete the call. You didnt have that symptom so I agreeed it might have been a ring generator problem. Theres at least two generators in a remote and they might balance the calls between them, depending on the system.

You get CID info because that is sent before ringing starts

Last edited by Noobed2336; 03/27/20 11:46 PM.
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Re: Interesting call. No ringing voltage
Noobed2336 #636128 03/28/20 03:49 AM
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Actually, CID data is sent between the first and second burst of ring battery. The first ring 'wakes' the CID unit to prepare to receive the data and process it, then by the second ring, the data is presented. Most phone systems have the ability to filter, or ignore the first ring burst so that the phones don't ring until the information is ready for display.

Chris, yes there are pair gain systems located underground in CEVs (Controlled Environment Vaults), which may have been what they were speaking of. Also, as Noobed2336 said, a very high-resistance fault on a cable pair, usually underground, can cause all kinds of strange issues. Glad to hear that they got this resolved and thanks for letting us know the outcome.


Ed Vaughn, MBSWWYPBX
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Re: Interesting call. No ringing voltage
ChrisRR #636150 03/29/20 05:50 PM
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No problem, Ed.

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Re: Interesting call. No ringing voltage
ChrisRR #636175 03/30/20 09:10 PM
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Reminds me a bit of a service call I did on a Rolm 8000 PBX about 5 years ago, Yes, the customer still had a Rolm 8000, and it was all analog. The VRU wasn't answering, I had the customer call another ext. and have someone answer, audio was good. It sounded like no ring voltage. When onsite I checked the fuses, they were good. Thinking that would be the case, I brought an Elgin 1A2 power supply I had at home that provided 90V ring voltage. I wired that in, it ran like that for a few weeks until I got a replacement power supply (that weighed about 80 lbs).

In the fall of 2015 we finally replaced the 8000, with a Rolm 9751, so now the system was only about 20 years old. To them it was a huge upgrade having digital phones, and we were able to connect the T1 directly to the PBX instead of a channel bank with 6 wires per tieline. The store has recently closed, like many others in the chain.


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