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Voip telephone ringing signal, trying to make a rotary phone ring!
Posted by
belzrebuth
on 16 Sep, 2022 00:34
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I was trying to make an old Ericsson cobra phone ring to incoming calls to no avail.
At first I thought there was a problem with how I wired the ringer on the phone itself but now I'm sure there's something else at play here.
On an old-school telephone line there should be a 90 (or thereabouts) VAC ringing signal when someone is calling you which is plenty for the buzzer to do its thing.
But there's nothing showing on the scope when probing my VOIP phone line other than DC.
Not sure what's the equivalent of a ring signal on a modern line..I don't see anything when I call myself..
I tested the buzzer with an AC voltage of about 70V@20Hz and it rings so there's nothing else there preventing it to ring other than the line itself.
Is my project doomed to fail?I can talk to and hear the callee but what good is that if you don't know when you're being called.
I was looking for some kind of trigger or something but it's just DC..
Really hope that I've missed something!
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#1 Reply
Posted by
ledtester
on 16 Sep, 2022 01:17
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#2 Reply
Posted by
Nusa
on 16 Sep, 2022 01:22
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VOIP is basically messages over the internet. Triggering a ringing event when a call addressed to you is waiting to be answered would be a software event. Which one then uses to trigger a hardware action. It's not something you can "see" by looking at the raw signal without decoding.
If you're not working at the API level and have a piece of hardware and/or sealed software package instead, you're probably out of luck if it doesn't provide such a feature.
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#3 Reply
Posted by
Peabody
on 16 Sep, 2022 03:28
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What phone do you normally have connected to your VOIP line? Does it ring? Do you possibly have some kind of call blocking set up on the VOIP line that's causing the calling number not to ring?
I have an Ooma Telo VOIP system, and it definitely generates the ring voltage. And the Caller ID packet.
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The thing to consider here is what VOIP stands for, which is Voice Over IP. On packet level there is the negotiation part that uses TCP/IP packets, and it is within these that the ring command is send. The voice part uses real time UDP packets.
To make it work with an older analog telephone you need a conversion box. This box is attached to the network on one side, and on the other you can connect your analog phone. Not sure if these still use the 90VAC to make the phone ring.
Or you can have an actual VOIP phone, which directly connects to the network. In this case there is no connection for an analog phone.
Most phone connections that nowadays are called VOIP are terminated in the internet modem and are converted to analog phone outlets there. Not sure if these use the 90VAC either. In this case most internet service providers don't share the VOIP information with the client and you can't connect a VOIP phone to it.
So the question here is what is it that you are using and try to connect to.
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#5 Reply
Posted by
jonpaul
on 16 Sep, 2022 05:39
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Ring POTS line 90 V 20 Hz in USA.
Make a 90V 20 Hz bridge inverter, use a transformer or drive direct
Viking Electronics model DLE-200B
j
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@jonpaul,
I don't know what you get on the vikingproductstore page, but I get shit with porn on it, so check it please.
Also the musson link seems a bit of advertisement for theater equipment?
Edit: this is the correct link:
https://vikingelectronics.com/products/dle-200b/
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#7 Reply
Posted by
tooki
on 16 Sep, 2022 06:17
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I was trying to make an old Ericsson cobra phone ring to incoming calls to no avail.
At first I thought there was a problem with how I wired the ringer on the phone itself but now I'm sure there's something else at play here.
On an old-school telephone line there should be a 90 (or thereabouts) VAC ringing signal when someone is calling you which is plenty for the buzzer to do its thing.
But there's nothing showing on the scope when probing my VOIP phone line other than DC.
Not sure what's the equivalent of a ring signal on a modern line..I don't see anything when I call myself..
I tested the buzzer with an AC voltage of about 70V@20Hz and it rings so there's nothing else there preventing it to ring other than the line itself.
Is my project doomed to fail?I can talk to and hear the callee but what good is that if you don't know when you're being called.
I was looking for some kind of trigger or something but it's just DC..
Really hope that I've missed something!
Just to clear up terminology: by “VOIP phone line”, do you mean the analog phone jack of some VoIP device? If not, can you elaborate?
Assuming you do mean an analog jack on a piece of network equipment (such as your ISP-provided modem/router), please provide the model number so we can look up the specs. Maybe it’s outputting a much lower ring voltage (or current) that’s enough to trigger an electronic ringer, but not ring a mechanical bell.
(A VoIP “line” doesn’t really exist as such. It’s packet-switched, not circuit-switched, using TCP/IP and UDP, with VoIP phones typically being connected via Ethernet or Wi-Fi.)
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#8 Reply
Posted by
belzrebuth
on 16 Sep, 2022 09:41
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https://openwrt.org/toh/vodafone/vodafoneh300sThis is the router I'm using, it is provided to me by the service I didn't choose it or specifically bought it.
It's plugged straight into the wall and has two phone rj11 outputs.
The phone plugs into the first one, the other plug marked #2 doesn't work AFAIK maybe it's for a second phone number.
That's the whole setup!
If I try to to plug the phone straight into the wall with an adsl filter it doesn't work.
That was the older configuration, the way to have a landline now is to pass thru the router that's why I wrote it's a VOIP line, not sure about the details though.
Edit: I enabled the second phone output on my router and plugged the phone there and bam! It rings.. really don't know why it works but it works!
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Your provider clearly upgraded from analog telephony to digital telephony. On ADSL there are two possibilities. It is either a separate digital channel on the phone line, or it it true VOIP, either way the modem should provide a proper ring signal for an analog phone. I have no experience with very old phones with mechanical bells for the ringing, but have used analog phones within similar setups and never had them not ringing.
But it might be that your provider did not configure the modem properly.
Since you linked to openwrt, it might be that you upgraded your modem to this software and that it has a bug. Or that you missed something in the settings.
Edit: It seems you solved it while I was writing my post
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#10 Reply
Posted by
belzrebuth
on 16 Sep, 2022 10:04
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It seems that the phone 1 output is missing the AC voltage somehow, I can clearly see the 24.9Hz 90VAC signal when the telephone is ringing when probing output #2 but nothing shows on output 1.
Maybe output 1 is for a cordless phone and 2 for a rotary phone
Anyways now off to figure out how to actually make a call..!
I think there are plenty of ways for that on the net.
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I'm not an expert on why but with AT&T newer gateways/modems most rotary phones and newer phones that have pulse dialing will not work to dial out. I believe it has something to do with dtmf type tones are the only signal that can be interpreted digitally.
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#12 Reply
Posted by
tooki
on 18 Sep, 2022 12:08
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I believe it has something to do with dtmf type tones are the only signal that can be interpreted digitally.
As a blanket statement that’s clearly nonsense, since digital (as in, computer controlled) telephone switching equipment has been in use since the 1960s, with full backwards compatibility with pulse dialing.
The people designing the analog jacks on VoIP gateways probably just concluded they could save a few cents by eliminating the circuitry and/or code to decode pulse dialing, since it’s not likely to represent a significant percentage of users. Or it’s even possible that the equipment can do it, but the telco simply disabled that feature so as to not have to provide technical support for it.
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#13 Reply
Posted by
fordem
on 19 Sep, 2022 14:30
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Google REN or ringer equivalence number - you'll at least have an explanation for why it's not ringing.
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#14 Reply
Posted by
belzrebuth
on 25 Sep, 2022 16:10
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Still struggling with this!
I'm now in the process of trying to make it make calls and I will call it a wrap.
I built a board of this project here :
https://www.mattmillman.com/projects/building-your-own-pulse-to-tone-converter/But I have no clue where the pulse and dial contacts need to be connected on my phone.
I'm lucky enough to have the schematic in a paper glued in the inside of my phone but I really find the schematic a bit weird to decipher..
I initially thought that the dial and pulse points would be points marked "1" and "13" respectively but these points don't go to GND when the shunt goes closed or open..
Of couse I've tried various other spots but I've yet to find a combination that works.
Any help would be appreciated as this is getting annoying..!
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#15 Reply
Posted by
Peabody
on 25 Sep, 2022 22:37
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My memory is that pulse dialing is just breaking and remaking the connection back to the central office. In fact, you could dial a number by just flashing the hook switch at the right speed. If that's correct, then the main twisted pair would be the lines you want to connect to.
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#16 Reply
Posted by
David_AVD
on 25 Sep, 2022 22:58
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The design given in the link
https://www.mattmillman.com/projects/building-your-own-pulse-to-tone-converter/ seems to be based on modifying the existing wiring of the phone. It disconnects the dial disc from the phone line and connect it to the Attiny85 separately to be able to detect the pulses. The dial tones seem to be injected with the use of transistor Q1. I myself would add a series diode in the supply line to the Attiny85 instead of relying on the zener diode.
Which connections in the schematic of your phone are for the dial disc is not clear to me, but it should be easy to detect by looking at the phone and follow the wires.
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#18 Reply
Posted by
belzrebuth
on 26 Sep, 2022 10:56
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As I understand it I need to find a point (pulse) which connects to GND or the (-) point of the incoming pair when the dial is turned clockwise and shorts "n" times according to what I dialed in.
I found that point where the dial when turned clockwise remains solidly shorted to GND and when the dial is left to freely rotate it shorts in clicks as per what number is dialed in.This is the orange wire.
I also found another point (shunt) that connects to GND when the phone is picked up.This a light blue wire.
There are more than one points where there is blue wire but only one that connects to GND when the phone is picked up.
Orange is point "J" okay as per the schematic, the other one I don't know but it does what it should so I believe this is it.
Connecting those to the circuit doesn't work though so maybe I should break the connection somehow?
I just tapped on those and connected them to the MCU.
BTW I used the second simplified schematic and the zener loses its temper after I while.
I'm not sure it's a 1W zener but it certainly gets hot after a bit and votage begins to rise so I had to turn the circuit off.
Maybe a series resistor would help or I really need to use a 1W zener for it to better tolerate the current that passes through?
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I think it is best to disconnect the one end of the dial disc from the phone and only connect it to the circuit. Because you don't want the pulse signal on the line, you want the tones on the line.
For the zener diode, it depends on the voltage drop over the series resistor how much current flows through it. Then that current times the zener voltage gives the amount of power it has to dissipate. Since you are connecting to a analog port on a modem there is no long line in between and the voltages might be a bit high. So measure them with the phone on the hook and with the phone of the hook to see what is needed in your case.
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#20 Reply
Posted by
belzrebuth
on 26 Sep, 2022 12:38
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Thanks so much for your help pcprogrammer.
I'll try to disconnect the dial from the line what you say makes sense the circuit needs the pulses as inputs and the line needs the tones from the microcontroller.
Also, I think that my readings are wrong, it's not the zener (while it gets a bit hot).
I have 5V on the MCU when no other signal than line(+) and line(-) are connected as V+ and GND but things get messy when I'm playing around with other wires that most of them carry a 29V(!) or so potential to GND.
Connecting those to the attiny was definitely messing with my readings; it's a miracle nothing happened to the attiny so far.
I'll try putting some sense into this and post back.
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#21 Reply
Posted by
macboy
on 26 Sep, 2022 12:41
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...
BTW I used the second simplified schematic and the zener loses its temper after I while.
I'm not sure it's a 1W zener but it certainly gets hot after a bit and votage begins to rise so I had to turn the circuit off.
Maybe a series resistor would help or I really need to use a 1W zener for it to better tolerate the current that passes through?
You absolutely need a serious resistor. Did you forget to install R1 220 Ohm? I would look to increase this to more like 470 ohm, maybe higher. The 220 ohm allows too much current, well over 200mA. This means well over 1 W dissipation on the Zener unless something is constantly using much of that current. The microcontroller itself is not.
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#22 Reply
Posted by
belzrebuth
on 26 Sep, 2022 12:59
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I don't see any resistor on the schematic I'm using.
It's a bit further down the page and it's using a 27V zener instead of the 5v1 on the first schematic.
I'm also used in the typical vcc->resistor->zener->gnd scheme but this circuit is a bit different.
It seems to be using the zener without a resistor as rough limiter of the regulator input voltage.
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#23 Reply
Posted by
Nusa
on 26 Sep, 2022 13:24
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Correct, old rotary dials do mechanical switch pulsing on the release, not when your finger is winding the spring.
And it was technically possible to dial only using the hook switch to create pulses. 10 pulses per second is the target, but the actual tolerance of analog phone systems was generous enough that a practiced human could get close enough.
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#24 Reply
Posted by
rob77
on 26 Sep, 2022 13:49
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