How to amplify an optical phone ringer?

Thread Starter


Joined Apr 13, 2017
Hello all

For over two years now, I have an optical cable line with internet, TV and phone services. Before I had ADSL. It is better and everything runs perfectly, but the phone ringer.

I have a hearing deficiency following a bad flue a few years ago. I can hear low frequencies almost normally, but after a certain point my hearing graphic starts dropping in a very steeply straight line and I can’t hear the highest frequencies at all. I understand the highest human listening frequencies usually drop with age, but in my case the problem is not that (only the highest), but as the graphic I said shows. No need to put it here because it is exactly as I described. I cannot hear the microwave oven beeping when it stops, but as I can hear its low frequency motor working, even if I am not in the kitchen, I know it stops when the motor sound stops. This does not let me hear the phone ringing with middle to high frequencies if I am not close enough.

I used to hear it when I had analogic ADSL because the sound was strong enough, but with this low voltage fibre does an old bell phone ringer does not do more than clicking, really. I have tried several modern phones, but their sound is always too weak for my hearing capabilities.

I also tried to use ringer amplifiers, but then, there is another problem. I could not find one for optical cable. Some, with a power supply (I bought one of those), are advertised for a ringing sound level of 100 dB. Maybe they do that on analogic lines, but on fiber they sound as the other phones I bought, the same weak sound.

There is an obvious solution for this – go back to ADSL with an analogic phone line – but that is exactly what I want to avoid. Hence, I came here in the hope of an advice on how to amplify a phone line ringer. I did not measure the voltage because I am sure it will be very low, far from the 50 Volts I had on the old line.

Thank you very much for any helpful suggestion.


Joined Dec 29, 2008
... not too familiar with optical fiber phone service.
When the phone rings, is there any type of unique signal that occurs ... a light, a noise ...which could activate some device that would be more easily discernable?
This could be just a LED diode, a buzzer ...but needs to be particularly associated with the phone ringing.

Thread Starter


Joined Apr 13, 2017
Thank you for both replies. I had further reading searching the forum with "sound activated relay" and other links from there.

On the phone nothing changes when it rings, except that it rings, the same as with analogues. As I said, I bought a mains ringer amplifier with phone line through, IN and OUT. I does have a light that strobes when the phone rings, if powered, but it is not the solution because during the day it is not really visible from another room with the day light. It is not of much use, and if not useful, I better keep it disconnected not add another charge to the line, and at night the light is not that strong. Even over night it is rarely is visible from another room.

A sound activated switch might do the job. If close to the phone, it could be activated by the phone ringer itself, but I need power to connect and operate a bell, which I actually do not not have close to the phone. That is why I have been looking for a way to amplify the phone power instead, which I could place anywhere wherever the phone line (coming out from the router) passes close to a power line. Then, there, I could replace the (router) phone line with the amplified version and an old analogue telephone would ring as before.


Joined Dec 8, 2016
I normally just ask the questions. However 20 yrs in telecomm this grabbed my eye. You say you have an optical cable line. Fiber to the home. Amplifying fiber/light, probably not something you want to do nor should you have to. Your other services work well and you made no mention of pixelation on your tv's. The unit that goes from fiber to analog phone jacks... The "box". Why can you not simply amplify it. You should be able. Its simple analog on a twisted pair wire at that point. Maybe its the devices you have tried? how they are tied in? Dicks idea to me. Sounds as easy as anything. I have seen remote controlled outlets at the dollar store. I am almost positive there should be some relatively nice and inexpensive user-end solutions 2017. 10-15 bucks

I did not look into these devices well but, this is where I would start.

The latter can be found cheaper. Configured and simply placed next to the phone. You hear every call. Way more advanced options are available dirt cheap as well. Could alert your mobile phone, Send you and e-mail, Set off your fire alarms lol, about anything you can think of.

Also with this setup I gave you the links for. I am thinking you will be adding an audio file of your choice. That could be fun/funny.

ian field

Joined Oct 27, 2012
Maybe the simplest solution is a sound activated relay that can turn on a lamp, buzzer, or bell.
Some older ringers were mini speakers with a voice coil that radiated enough magnetic field to detect - but I think they're all piezo disc now.

A good guess at the size of the piezo disc would give it close enough resonant frequency to be sensitive to the ringer sound - and not so much for ambient noises. A twin-T filter might come in handy to sharpen it up a bit more.

Thread Starter


Joined Apr 13, 2017
Thank you for your suggestions jgreene44. I had not found them before, maybe for not searching with the right terms. I had a look at those eBay links. The second link does a lot of things, I only need to make a bell ringer work and the shipping is about $36, a bit too high, so I think I will order the one on the first link.

Sorry if I am not skilled to electronics, and I have not touched them for too many years. I don’t have the circuit with me yet, of course. I’ve seen the connecting points, but there is not a picture with the connections like the one on the other link. Do you think that after receiving the circuit I can ask you then, if this is not bothering you too much. The order will only arrive between mid-May and after mid-June, according to the eBay seller. Again, all I need is to make a bell ringer ringing with an incoming phone call. I initially wanted to amplify the phone line voltage, but any other way that amplifies the ringing sound will do for me. Do they power ancient phone bell ringers working at 50V?

About the pixilation you ask, if you refer to my TV resolution, it is 1920 x 1080.


Joined Dec 8, 2016
Pixelation is just a term used in the industry. Basically your digital image will be displaying the individual pixels improperly and, you can easily see this. This is an excellent indicator of anything less then good quality signal to your home.

I actually spent a few and looked at those items since you talk of maybe actually ordering these items.

The first link. Yes that alone could work. 5 bucks too! I do not believe that you will have too much problems with using it.
Very strait forward. And yes with a little help and, I would be glad to help. Only problem is you will have to plug it in to
something/anything that stays on and makes a load noise/ring.

This is why I gave you the second link and, yes. This will require much more know how. You could handle it but,
I understand if you do not want to go through training just to make your phone ring lol. Instead of this you can find many other options on your own. Anything you can plug in that makes noise and stays on I assume.

If you still feel overwhelmed by this. I would be willing to build you one at no cost that would arrive as a simple plug and play.
If not for packing it up and mailing it. So Im kind of hoping you go with option one. But I also thought about a gift exchange! There are plenty of cheap little e-bay items I could use too. Could be fun.

I want to add this also. If you are at all interested in the second item less the price. You may have missed that part about this one being overpriced. Idk perhaps I failed to state... Here is one. I just had to look. 2 dollars lol! Appears to be more strait forward as well!

Whatever you decide keep us posted. I am interested and hoping you get your problem resolved with little trouble or expense.
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Joined Aug 1, 2013
Are you asking about a circuit you can build, (ring signal detector, low frequency oscillator, amp, speaker)
advice on a commercial device,
or maybe a couple of ebay modules you can wire together without any circuit assembly?

There are many ways to do this, but the inconvenience of not having AC power near the phone will be a common issues with most of them. One solution might be to get an old phone with a real bell ringer inside, and let us steer you through disabling the phone part and keeping the ringer. Can you hear an old style telephone bell?

Referring to a piano, what is the highest note you can hear clearly from another room? For example, A above middle C (A4) is 440 Hz, while the C two octaves above middle C (C6) is a little over 1 kHz.

A circuit to do this could be as simple as an LM386 (small audio power amplifier) configured as a 200 or 400 Hz power oscillator, enabled by the phone line ring signal (an opto-coupler). Depending on how often the phone rings, the whole thing could run for a year on one 9 V battery. Or (getting cute here), since your in-house phone line isn't a real phone company phone line, you might be able to use it to trickle-charge an internal battery or supercap. Actually, that sounds like something that might sell...

Where are you located?

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Thread Starter


Joined Apr 13, 2017
I was writing this, but I had to go out without posting (left the computer on sleep and it stayed here), and on on arriving I had an e-mail announcing your reply. There is no need to delete it and restart anew, but just add some more.

I found a wiring diagram for the sensor on your fist link. It is convenient because it has a sound pressure sensor and a photo-resistor already on board, but I couldn't find anything about the output on both diagram or texts I read. I fail see how the output will make an old 50V phone bell ring.Sensor.jpg
My hearing deficiency is at the best -30 dB and goes slowly down until 1 MHz at -40 dB. Then, is drops on a not perfect line at roughly 130° with slight differences between right and left.

It is really kind your offer for you guiding me through this. For many years now, I am not so close with electronics, and because the best local shop closed over a year ago now, it is very difficult finding anything but components (popcorn and olives). I think the only problem will be with the output, but probably it can only be solved a long time from now, according to the time the seller says the delivery will take. I tried to search for a quicker delivery, not that I cannot wait, but to not keep you waiting, but no chance. While searching, I found that circuit available from many place, with very different prices. The best description I found was on Aliexpress, but there too, not enough about the output.

Thread Starter


Joined Apr 13, 2017
Yes, AngloKid, I am looking for anything that makes me hear income phone calls ringing, preferably an analogic phone bell. However, there is not enough power on optical fibre phone lines to make a normal analogic phone bell ring, they just click. I used to travel and have phones from different European countries, none from Far East. They all used to work perfectly on an analogue line. They still do on analogic, but instead of ringing they just click, even the more modern pones with a buzzer or musical sound, buzz or play very low.

About my hearing, on my last post I said "1 MHz at -40 dB". It obviously was a mistake, I meant 1KHz. When I tried to correct I got an error message, the time to edit is only 10 minutes!

The phone is in the corridor/hall because of being central, so the best place to be heard in all rooms, but also the only one without an AC power wall socket. I can place any gadget all along the line wherever it crosses with the power line, not only close to the phone, but that does not seem to be possible.

crutschow, please don't ask me how or why, but modern phones on an optical fiber line work on rechargeable batteries (usually AAA) charging from a base connected to the mains and do not need external power even for hands free. In my case they ring too low and I wanted to use an old phone with bell, but on the fibre line they don't ring, just ckick.
This thread is going all over the place right now.

There are two major issues:

The ONT has a REN or the amount of ringers the device can drive,

Quote from here:

If you have old phones (WE 500 sets) you may have problems. My ONT can just about ring one WE 500. I called them about this and they said it is within their parameters which is wrong of course. I am only asking for 5 REN which is what they have been providing for decades.

So the typical REN for analog lines is about 5. This guy says it barely drives one model 500 telephone set. That is about 1 REN. There is usually a 1/2 ringer somewhere (the NID) in the system or it could be there from the old lines.

so, that's basically the reason it's not likely to work.

Probably getting the REN limit from your fiber provider will be like pulling teeth, They likely expect one modern phone which can be 0.1 REN.

The 1/2 ringer (0.5 REN) is there so the system can be tested with no phones plugged in except the artificial load.

The REN should be listed on the phones, except the really old ones. Real bells are probably a REN of 1.

So, you add them up. Include any stationary bells and add 1/2 ringer which is usually there, This has to be less than the drive capability of the interface.

If it's not - click and not a full ring as your hearing.

So, you should use your most modern phone with the lowest REN and connect it directly to the ONT I just checked a 4 station cordless base and the Ringer Equlivelence is 0.1B for all of the phones combined, so a style 1960's phone is worth 1 REN and 10 modern phones is worth 1 REN.

The ringer power supplies cost money, hence you don't get 1960's performance.

So, if you remove all the other phones and just connect your lowest REN phone, it should ring normally. Yes, there could be wiring problems within the home.

List your phones. Remove any DSL filters as well. A single splitter is OK. If they are connected wrong, your phones won;t ring. There's probably 12 phone things in the house. Don't forget FAX machines and analog modems.

You would likely need a Ring Booster II from here: The booster goes between the ONT telco port and the house telco wiring.

At a minimum do add up the REN's and do try only one phone thing with a low REN.

I too suffer from hearing issues. Tinnitus. A dip at precisely 2600 Hz. So, the alarm clock was replaced by a piezo buzzer that has to be aimed at me. There were lots of lost ATM cards.

There should be other devices that can convert ringing to a light flashing etc. We actually have two bell only devices. One was installed by the telco company when modular phones first came out so the phone could be heard in the basement. A ringer was added in the laundry room.
In some cases the ringer was disconnected on early phones, so it looked, for the most part, as two phones.

The last trick I did, was to use a baby monitor and place the "baby side" near a cordless handset. It does TRY to amplify everything in the room, so you need to put it where privacy isn't an issue.

We now use paging a lot at home because my elderly mom is in a wheelchair. I don't always carry my cell and sometimes i can barely hear it and you only get 3 rings to answer it. I can hear outside call rings and pages upstairs with no issues (3 cordless phones). The porch has a standard phone, so only outside calls.

Downstairs has two ringers, One in the laundry room and one in the cellar/2nd Kitchen. There were a few modems down there too.
BUT, the cordless phones have the PAGE option. So, the baby monitor is placed near a basement phone and the "distinctive ring' is also heard in the laundry room. I have to walk a fair distance to pick up that phone, but at least I can hear the page.

I hope I didn't make it too complicated.


Joined Dec 8, 2016
"I hope I did not make it too complicated" that really is humorous.

You asked about the output. There really isnt an output. The sound the device picks up will trigger a relay that would in this case be wired to an always on device. A basic but not really good example would be an alarm clock that left in a state that would leave it to where it would be on and load as soon as you plugged it in. that way when the relay is triggered whatever is plugged in makes noise for you.
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. While searching, I found that circuit available from many place, with very different prices. The best description I found was on Aliexpress, but there too, not enough about the output.

The sound switch "listens" for a sound that probably occurs for greater than a certain amount of time and provides a ""dry contact" (SPDT) or single pole, double throw that changes when either a light or sound threshold is exceeded. To disable the light sensor, you tape over it.
To power it with a voltage <6V, you insert the "jumper" or what they call a cap. For 6 to 30 V, you remove it. The light tells you to remove it, This is how I interpret the Chinglish. (Chinese English).

So, you would place this device in a case next to a phone "that rings" and is louder than the surroundings and connect it as if it was a switch to some device and power source that you have.


The REN amplifier that I suggested would go in series with the output provided by the optical box before it gets to ANY phone. This will make up to 7.5 old phones ring.


Something like this device really just plugs in like an answering machine. To bad they don't tell you REN or what frequency the sound it makes is at. 98 db at the wrong frequency won't help you. The flashing light will.


Your right, that the cordless type of phones have a rechargeable battery. Mine have 3 AAA type batteries. The power that those batteries can supply determine the loudness. The "baby monitor" that I have doesn't ring as loud because of the two AA cells. So, the sender is in a room where a TV might be and the receiver somewhere else. Can I hear the TV clearly - Nope. The receiver has lights too, but it doesn't help if I'm not looking at it. So, for me, I need to distinguish a "page" from an "outside call" ring and connecting to the telephone line won't help me.

The tiny bit of ring voltage is detected in the base station. That is 1/10 of what a model 500 phone uses.

The cordless phones work when there is a power fail, because of a UPS battery backup at the base station.


Any modern thing with external power is likely to require low REN. So, this might. I hate Amazon, Why? No datasheet.

Here you will find real data such as 0.5 REN, the frequecies and the sound level with "A" weighting (The response of the human ear).


Joined Aug 1, 2013
According to the datasheet the lowest fundamental frequency is 700 Hz. This might be too high for this application. Also, I don't think explosive-environment housing is necessary.

At least there was a datasheet. Your not going to see a spectrum analysis of a telephone ringer that you can match up against a hearing response test which may be ultimately what the OP/TS needs.

If you do have a cordless phone that you can't hear and don't have a phone line nearby, you can always use one of these: but it does not tell you how many bells it can drive, but it draws 0.7B from the phone line. Extension units would presumably have their own drive ability.

So one "transmitter" would draw 0.7B and each "receiver" would have yet another number of "phones" it could drive. You could just use the receivers for Bells if you wanted to near cordless base units.

This or multiple units of
WB-SAHORN Sonic Siren

The Remote Horn, model RH 100 adjustable remote horn will alert you by sounding an adjustable tone and volume control, which allows you to select the most effective audio alert sound combination. From a loud 78-85 decibel low frequency to a high 113 decibels. The adjustable tone ranges from 200-2,000 Hertz.

when combined with the Sonic transmitter (e.g. TR55) might actually be your best option. Here you can actually select the frequency of the ring.

So, there are all sorts of options to sort out.

Knowing the REN of all your telephone devices and knowing the REN that the Optical gizmo can drive would be a big help. You or someone else can try to empirically determine it. Add/subtract phones until it rings and doesn't ring and keep track of the total REN.

Remember to keep track of everything. If the optical guys used an existing box, it may take 0.5 REN's just being there.

As you can see from here: NID's can have 1/2 ringer modules in them.