Plain Old Telephone Voltage

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iwire

iwire

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OK have another job that will not die.

We do security system repairs for a national alarm company. I was sent to replace the mother board in a panel because they could not stay connected to it via phone lines. When they called in the panel 'answers' connects for a short time and then dumps the call. So I install a new panel and the same problem happens, the alarm company's tech support thinks it may be the POT line. So the telco has been out and says all is fine.

So now tomorrow I have to go back to the site and meet the phone company so we can work together to find a solution.

On a previous trip the alarm company had me measure the voltage on the phone line when they called the panel here is what I had

Idle 45 volts DC

Ringing 90 to 100 volts AC (my meter switched to AC anyway)

Panel picks up 5 VDC.

Do those figures sound right?
 
Yes Bob the numbers sound fair but a little suspect.

A Telco plant nominal voltage is 48 volts. On hook should be around 50 to 54 volts. Remember our charger discussion? :D

Off hook voltage depends on the cable distance from the plant of anywhere from 5 to 20 volts. Current is limited to 60 ma maximum at close distances on the plant frame with a direct short. 10 ma is normal current. 5 volts @ 10 ma is the minimum off hook voltage/current assuming you are some distance from the CO. So you might be a bit low if you are close to the CO.

90 to 130 Volts is plenty good on ring voltage.

If anything sounds like you might have some leakage to ground or a high impedance splice/bridge connection. I say this because your on hook and off hook voltage is a little low. If you have a butt set listen in the monitor mode, it should be silent, then seize the line (off-hook) and listen closely for HUM. If you hear HUM or power line frequency, it indicates a leak to ground from something like a cable protector or a bad splice/connection causing an imbalance picking up power line frequencies from induction. Carbon block protectors!!!!

Bottom line: If you do not have a butt set ,here is the nail in the coffin. Go to the demarc, plug in a plain ole telephone at the NIU that breaks the premise wiring connection or wire it up yourself, Go off hook and call someone, If you hear any buzzing, hum, or noise it is the TELCO line problem. If it works like your phone at home, it is YOUR problem.
 
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dereckbc said:
Well that settles another question, I will run out and pick up a new Butt set tonight. I am embarrassed to bring my rotary butt set in to work. :smile:

Thanks for the tips, is there anyway to check these carbon blocks. I think they are in the same room as the alarm panel.

Any chance it could it be a polarity issue?

Rotary is just fine but do not tell the boss or accountant. Best test is the Demarc (NIU) with the premise wirng diconeected. Doesn't matter if it is a butt set or a ole black 2500 telephone rotary dial like you had when 10 years old, it still works today.

Yes check those $!^& carbon block protectors. Pull them out and shine up the contacts on your blue jeans or replace. Gas and solid state are more reliable.

OOPS Bob wrong button, you get the point. I edited a mod :cool: Did not know I could do that.
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Bob to check the carbon block is just unscrew them, they are in parallel and should not break the circuit. Others are in series and parallel and will break the circuit.

Polarity depends if it is sensitive to it or not. Most likely not, try reversing.
 
Polarity should only matter when dialing, and most equipment of the last 20 years isn't polarity sensitive anyway (I very much oubt that the alarm panels are). Is the line coming direct from the telco central office, from a PBX, or from some sort of contcentrator? An open circuit of only 45vdc is defintely suspect IMHO, and some concentrators don't do well with modems.

One thing to try, although it's a pain, is a fax machine. Telcos usually don't care about modems ("they're computers, we don't guarentee the line for that"), but if a fax doesn't work, they're usually look at things.

BTW, some places consider a rotary butt set a badge of honor :D.
 
zbang said:
Is the line coming direct from the telco central office, from a PBX, or from some sort of contcentrator?
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It appears to me to be direct to the telco, but then again my experience with phones is limited and I would not know a 'contcentrator' if it hit me in the head. :smile:


One thing to try, although it's a pain, is a fax machine.
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I could do that and maybe I will before the tel co guy gets there. Thanks.


BTW, some places consider a rotary butt set a badge of honor :D.
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I bought mine when I was in high school from a phone guy that I imagine had just gotten his touch tone set. :smile: Mostly I used it to call the shop in the days before cell phones.
 
Bob, you might also try a temporary direct wire from the alarm panel to the NID, and see if the connection still drops. A process of elimination starts with the easiest substitution first.
 
LarryFine said:
Bob, you might also try a temporary direct wire from the alarm panel to the NID, and see if the connection still drops. A process of elimination starts with the easiest substitution first.
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That would be an easy check, I think the distance is less then 15' but I can not see the existing cables route so it could be damaged.
 
I had a very similar experience and it turned out to be the program running the alarm panel was corrupt. My alarm tech tried dialing the panel and install program over the phone but the line kept dropping. He had to bring out a lap top.
Thats how I understood it when I asked him about it
 
Update, went out there Tuesday AM and met with Verizon and the customers Telcom contractor, both pulled out butt sets listened to the line, made calls and pronounced that the Telephone line was not the problem.

I pressed on and got the phone guy to break out a meter and check for voltages ......... he ad a nice meter made for phone use but did not seem to know what he was looking for. He said it was fine.

So they left and I got on the line with Bosch tech support (The panel maker) they tried to call in as well got kicked of the line. Bosch said phone line trouble.

Got on the phone with the central station and they said they would try a few things on their end ..... still no luck.:mad:

At this point I am frustrated and stuck in the middle, so I ask the central station if I was to find any other phone line and give them the number could we try that? They said sure.

So seeing as I was in the customers phone room and they had many lines I hunted around until I found one that was direct and that I could call in and out on. Once I found it I cut it off whatever it was connected to and tied it into the alarm panel. Called the central station gave them the new temporary number and guess what .......... It worked perfectly with no problems at all.

Of course I could not leave it that way so I restored the 'stolen' phone line to it's original location and connected the alarm panel back to it's dedicated line ... and again it will not work. :D

So after more calls to tech support I left telling them they have phone line problems.

A few hours later I got an email from the site, they gave me a list of numbers I can use for the alarm system I will be going back today to find one of these numbers and tie it into the alarm panel.

This will make the fourth time I will have removed the old alarm panel and installed a the new one ......... but I am getting good at it ..... I can do it almost as fact as a NASCAR pit crew. :D
 
bob-


I've had this problem a many times. Exact situation. Verizon will not own up to the problem. Either its a problem with their system which we will never know, or it could be a ground fault on the pair the POTS line in the underground cable feeding from the pole to the demarc in the tele/comp room. I have had found a direct short to ground on the pair for the FACP phone lines. I request the customer to call Verizon and notifiy what I found. They come out, switch the line to another pair in the cable that is not grounded and tell the customer after testing it "NOTHING IS WRONG, its the fire panel."

It seems that the GF allows the panel to communicate for a while but eventually the GF wins.

Those guys are awesome!!:mad: booooooooooo verizon.
 
This is an analog phone line? Is there any chance that this is VOIP line? I have had a similar situation with Radionics panels and ATA boxes providing the phone line. You could dial the panel it would pickup but when you had to send any programming or upload it, it would kick you off. I did not know it was a VOIP system until I asked the IT department. They told me they had switched out their analog phones a couple of months before.
We ended up installing a Network communication module and have had no problems since.
 
MAK said:
This is an analog phone line?
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It is comming into the building but the Verizon man says it goes to a 'SLC 90' right outside the building. (I don't know what that means and he did not seem to know either)

I have had a similar situation with Radionics panels
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It is a Bosch / Radionics

You could dial the panel it would pickup but when you had to send any programming or upload it, it would kick you off.
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Exactly.


We ended up installing a Network communication module and have had no problems since.
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That was what Bosch tech support suggested. :smile:

I did not make it there today, I am supposed to go there first thing in the morning and cut it over to another phone line.
 
iwire said:
It is comming into the building but the Verizon man says it goes to a 'SLC 90' right outside the building. (I don't know what that means and he did not seem to know either)



It is a Bosch / Radionics



Exactly.




That was what Bosch tech support suggested. :smile:

I did not make it there today, I am supposed to go there first thing in the morning and cut it over to another phone line.
Click to expand...


The panel I was talking about was also a bosch 7412?
 
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