My landline is out, so like all good citizens, before calling the phone company I checked the box outside. I didn’t have a non-powered corded phone, so I put a meter across the terminals. 48 DC volts. So I assume the line is good.
Fast forward six hours, after crawling through various places, I took my laptop and modem out to the box. No dial tone!
What is the 48DC volts there if not a dial tone?
ETA: My cordless phone in the house defaults to “0 missed calls.” If I unplug the phone line, it reads “No Line.” It’s detecting something down there…
To add further information that may help. I have no DSL and DSL is not offered here. POTS only.
If I unplug the Telco side cable, all voltage is gone. I plug it in, I get 48V across the two terminals. I disconnect all other phone jacks and join it to the one and only jack I use in the house. At the junction: 48V. At the wall jack: 48 V. I even switched cables to my phone and plugged my laptop directly into this same phone jack. Changed phone jacks. 48 freaking volts.
Admittedly, I’m not a phone tech, but since I live in a rural area, I’ve used this test many times. When the phone is out, there is no voltage at the box. This time there is, and I fear that I am chasing my tail for something that is on the phone company’s side.
Also, if you try to call my number, you get a busy signal.
Funny and sad: The website of the phone company requires that I leave a phone number to call back to discuss my problem. I’m out of cell service range. Isn’t that like calling a plumber because you don’t have water in the house and him asking you to wash the dishes?
I’m fairly ignorant here (despite being the son of a phone line repairman), but I think the 48 volts powers the ringer. No dial tone means you’re not getting a signal from the phone company. If you’re not getting a signal from the switch, it doesn’t matter if you’ve got power to the ringer circuit.
Interesting. But doesn’t the phone company provide that 48V for the ringer? There’s only one line coming into the house. Is the dial tone signal segregated from the 48V ringer signal? No voltage drop accompanies the dial tone?
you want to test using a known to be good (keep a spare phone for just this purpose and emergencies) nonpowered corded phone on the phone company side of the box. the dial tone is put on top of the DC voltage. bad wiring or a bad phone can cause the dial tone to not appear.
the ring signal is 90V.
if a good phone on the phone company side gets no dial tone then notify the phone company.
if a good phone on your side gets no dial tone then you need to fix it unless you have a service plan with your phone company…
Yeah, I don’t have a cheapo old phone. Gave it to my daughter as a toy. But I did take my laptop with a 56K modem and plugged it into the phone company’s side of the box. No dial tone. So, that’s on them, I hope.
I wish I knew that a line could have 48V and still not have a dial tone before I pissed around with the phones all morning.
Not sure about the 48v, but I had an episode with a very rural phone this summer that at first was scratchy but working. Then you could call in but there was no dial tone. I always thought that no dial tone = dead phone. The phone company came out and found a wire that was broken, but touching on their side of the entry box, and another wiring problem in a pedestal box about a 1/4 mile away. The tech re-punched the wires and that resolved the problem
POTS is surprisingly complicated considering it only uses two wires. It’s a pretty darn creative use of minimal parts and wires if you ask me.
The ring signal is 90 volts AC at 20 Hz. It is only present when the phone is ringing.
The 48 volts DC serves two purposes. First, it lets the phone company’s equipment know if you have picked up the phone. When you take the phone off hook, you connect the circuit and draw current from the 48 volts DC.
The 48 volt DC supply also provides the voltage source that drives the voice signals. The voice coil modules the current going through it to generate your voice signal going out, and the current is modulated by the phone company to provide the voice signal coming in. A specially wound coil of wire makes it so that the voice signal from your own voice isn’t as loud in your own earpiece. Pretty creative for a bunch of simple magnets and wires, and modern equipment, though drastically different in its implementation, is still compatible with it.
Getting back to the OP.
On most modern phone services, there’s a jack right at the entrance bridge (where the phone wires come into your house). Plug an old fashioned simple phone into it. If it doesn’t work, then the problem is on the phone company’s side and you’re done. Call them and have them fix it. If it works, though, then the problem is inside your house somewhere and it is your responsibility to fix it (unless you pay for repair service from the phone company as part of your regular bill).
If you have a bad connection somewhere (like a corroded connection for example) it could be preventing enough current from going through to trigger the phone company’s equipment and make it think that your phone is “off hook”. It would still measure 48 volts DC when off hook since there’s no current flowing to drop the voltage.
