POTS Dial tone but no bill.

[electrofelon]

I was testing an old 200 pair copper line to try and determine it if there was anything active on it. I got about 50 volts on six pair. I didn't have a handset, but I'm going to assume that means there's dial tone. Now I was talking to an engineer at that telecommunications company about this line,. And she said they showed about a dozen active pairs on that line but then said they might not actually be in use. I asked if they could cross reference those numbers with accounting/billing to see if or who was getting a bill and she said she didn't have access to that information.

I did some additional testing and found out these active lines didn't go anywhere.

Okay now to my question. It would seem if you have a dial tone then its an active line and someone is getting billed for it. Has anyone heard of a line having a dial tone but not being in service?

 

[electrofelon]

Also it's just rather fascinating/ridiculous they couldn't tell me anything more about these "active" lines that might not be active

 

[zbang]

Having "talk battery" on a line doesn't mean you'll get a dial tone, a line that's connected to the switch but out-of-service could still get battery. Or many types of private lines would also have battery but no DT (e.g. "automatic ringing private line" and some data lines). The only way to tell is to listen to the line and maybe try dialing.

 

[petersonra]

I think your best bet if you really care is to get a handset and see if there really is a dial tone. I'm not sure that a dial tone by itself means the line is active.

I have heard stories about phone lines that are active and can actually be used to make phone calls that are not being billed to anyone. I don't know how true they are.

I know years ago a company I worked for had a new phone line installed to use with a fax machine. was about 1982 I think. The phone company installed it and somewhere along the line someone realized that we had not been billed for it for several years. I don't know if they ever told the phone company about the billing discrepancy or not.

 

[LarryFine]

Try a phone. If you get a dial tone, call your phone, check the caller ID, and try calling it back.

 

[electrofelon]

But isn't the 50 volts DC essentially the dial tone? I don't see how you could have 50 volts DC but no dial tone.

 

[GoldDigger]

But isn't the 50 volts DC essentially the dial tone? I don't see how you could have 50 volts DC but no dial tone.

Simple
The audio dial tone is sent out on the line and a dialed number detector is assigned to the line when an "off hook" condition (a DC load drawing sufficient current) is detected. Before that the only thing (if anything) being checked is line current. This avoids tying up expensive resources on an idle line.
If you had a lineman's set (butt set) you would hear a quiet line on AC coupled audio until you flip the switch to create a DC load. After a timeout of dial tone with no dialing the audio will be connected to an escalating source of noise and the number register will be used for another line when needed. To really save resources, the DC will eventually be removed too except for a periodic check to see if the line is still failed.
If the line is indeed active and someone dials it, the DC will be replaced with a DC-biased 20Hz 90v ringing signal. While the line is ringing, touching it is a bad idea and a mechanical voltmeter on the 50V range might be unhappy.

There is probably always a current detector on the line when "battery" (48V DC) is applied, but on an inactive line it will not do anything.

Sent from my Pixel 4a using Tapatalk

 

[electrofelon]

Try a phone. If you get a dial tone, call your phone, check the caller ID, and try calling it back.

Yeah that would make the most sense and answer all the questions. Unfortunately I didn't have a phone, kind of hard to find one these days . Anyway the network interface boxes have been removed and thrown in the recycle bin, and the 200 pair cable has been cut off, it's just an academic curiosity at this point.

 

[LarryFine]

I have a couple of these I used to use for troubleshooting:

 

[hbiss]

Having "talk battery" on a line doesn't mean you'll get a dial tone, a line that's connected to the switch but out-of-service could still get battery. Or many types of private lines would also have battery but no DT (e.g. "automatic ringing private line" and some data lines). The only way to tell is to listen to the line and maybe try dialing.

But isn't the 50 volts DC essentially the dial tone? I don't see how you could have 50 volts DC but no dial tone.

No. The 48VDC is talk battery that essentially powers the phone. You will get dial tone when you start to draw some current off the 48V like when the phone goes off hook. Dial tone is a 440Hz tone put on the line with the DC to tell the caller the system is ready for dialing. However, as zbang says, there are many services supplied over POTS lines that don't use dial tone and actually some that use much higher than 48VDC like carrier. Many times an out of service line or pair will still have battery on it. There will be times where there is a dial tone available but taking the phone off hook or dialing will not "break" it because the line is out of service also.

If you are curious, get yourself a butt set. Only way to tell and if you do any telephone wiring you should have one anyway.

-Hal

 

[electrofelon]

Learn something new every day.....thanks for all the info guys.

 

[Todd0x1]

It could also be a bridge tap in the OSP somewhere where you ended up with an unintentional branch of someone else's line. I had that happen once.

 

[hbiss]

It could also be a bridge tap in the OSP somewhere where you ended up with an unintentional branch of someone else's line. I had that happen once.

Happens all the time. You have to be careful when you are ripping out old wiring because a pair might be connected to a customer down the street. This is especially common with phone company terminal cabinets in private spaces of commercial buildings. You could go down the row of binding posts and find many working pairs. They may be abandoned or they are bridged with a line somewhere else. Shorting one will interrupt service to that customer.

-Hal

 

[tallgirl]

Another possibility, if there is no dial tone, is old leased data lines. The company I worked for in Dallas had one which came out the other end in Giddings, TX. We had a modem on one end, and a modem on the other, and what we put in on one end came out the other and that was that. But there was no dial tone.

 

[kwired]

Not so long ago had my land line number I've had for a long time re-assigned to a cell phone. My land line phone still had a tone when you picked up receiver, was a little bit different sounding tone than when the line was still active. IIRC if you tried to dial numbers it wouldn't break that tone.

Can't try it anymore, wife took the phone and either sold it or brought it to some thrift store I would guess. She good at getting rid of things if she doesn't think they are needed.