What are those three tone frequencies?

Thread Starter

MisterBill2

Joined Jan 23, 2018
8,711
In the US, when I dial an inactive phone number, get a loud three tone sequence followed by an announcement that "this number is not in service". The tones do not seem to match the touch-tone frequencies.
I want to try using those tones to discourage the constant barrage of scam callers. Maybe if their computer gets that message they will take me off the list. At least is seems like it is worth trying.
So does anybody know what those tone frequencies are? If I create a circuit to generate that sequence I will share it with everybody.
 

Alec_t

Joined Sep 17, 2013
12,060
If nobody here knows, you could try recording the tones and analysing them in Audacity.
I don't see how you would use the tones, since the caller will already have identified your line as active if you just replay them into the phone ?
 

Reloadron

Joined Jan 15, 2015
5,934
This should be what you are looking for. I tried setting them up in Audigy and they sound right. Note the duration is 330 mSec for all three tones and the frequencies are 950, 1400 and 1800 Hz. Will try and attach the .wav file. It won't let me.

The uploaded file does not have an allowed extension. The following extensions are allowed: .7z, .asc, .asm, .stl, .asy, .c, .cir, .csv, .djvu, .doc, .docx, .epub, .fzz, .gif, .hex, .inc, .jpe, .jpeg, .jpg, .lbr, .lib, .ods, .odt, .pdf, .png, .py, .rar, .sch, .sub,

Ron
 

djsfantasi

Joined Apr 11, 2010
7,689
This should be what you are looking for. I tried setting them up in Audigy and they sound right. Note the duration is 330 mSec for all three tones and the frequencies are 950, 1400 and 1800 Hz. Will try and attach the .wav file. It won't let me.

The uploaded file does not have an allowed extension. The following extensions are allowed: .7z, .asc, .asm, .stl, .asy, .c, .cir, .csv, .djvu, .doc, .docx, .epub, .fzz, .gif, .hex, .inc, .jpe, .jpeg, .jpg, .lbr, .lib, .ods, .odt, .pdf, .png, .py, .rar, .sch, .sub,

Ron
Rename it to have a .zip or other acceptable extension before attaching it. Note in your post that after downloading, it should be renamed back to .wav


I don't see how you would use the tones, since the caller will already have identified your line as active if you just replay them into the phone ?
But the phone company also picks up the line, doesn’t it? They need to connect to play their message.
 

jpanhalt

Joined Jan 18, 2008
11,088
On some telephone exchanges in the UK, the following audio message is looped for fifteen seconds, interspersed with special information tones (SIT), to advise the remote party has hung up: "(SIT) The other person has hung up". On iPhones, the tone is 3 bursts of 425 Hz tones each lasting 0.2 seconds.
In North America, the Precise Tone Plan used today employs two tones of 480 and 620 Hz at 60 i.p.m. (i.e. on for 0.5 s, off for 0.5 s). In the past, before the adoption of the PreciseTone system, busy signal was generally composed of the same tone as dial tone in the central office in question, interrupted at the same rate.
Source: https://en.wikipedia.org/wiki/Precise_tone_plan (and others)
 

Reloadron

Joined Jan 15, 2015
5,934
That worked. I made the download a zip and changed it to a .wav and it played. Been awhile since I have done this stuff. :)

Thanks All
Ron
 

Audioguru again

Joined Oct 21, 2019
3,171
I frequently get telemarketers in India (on the other side of the world) selling "Duck Kleening". They are so far away that there is a few seconds delay. I do not get telemarketers selling "Winders and Dores" anymore.

EDIT: I played your tones and they reminded me about the awful Amber Alert noises.
 

Thread Starter

MisterBill2

Joined Jan 23, 2018
8,711
THANKS to those who provided the frequencies. Since this will be generated by simple CMOS logic using some dividers off a crystal, and not played by a computer or smart phone, the frequencies are what I needed. The wave file will work well with a cell phone, though, for others who want to use it. My intention is to use some presettable down counters from some suitable frequency. So it is going to take a bit of math, which will be tedious but not hard. And the three tones can then be selected by DC control lines. So the final arrangement should be possible for others to duplicate.
 

Tonyr1084

Joined Sep 24, 2015
5,956
I've gotten all kinds of scam calls. I used to have a land line, but that was the most abused line. So because people I wanted to hear from had my cell phone, nobody was using that land line to call me. So when it rang I would sometimes answer it "Salt Lake Police. This conversation is being recorded. How may I direct your call?" That was often followed by a quick click. However pre-recorded messages still tried to call on that number. That's why I no longer have a land line.

On my cell, I have it set to only let numbers ring through that are on my callers list. The voice message says something like 'Sorry I missed your call. Due to a large number of scam and phishing calls unrecognized numbers will not be answered. Please leave a message after the tone.'

I've gotten calls from local police saying I had outstanding tickets. When I asked where their office was and that I'd come turn myself in for arrest - they stopped calling. Got a call from "The United States Treasury". Yeah, right. Like I'm sure THAT is legit. The voice spoke in the stereotypical Middle Eastern Asian vernacular (accent). So I said "Funny, you don't Sound like an American." After a brief pause he said "I'm from Canada." Yeah, he didn't sound Canadian either Aaye. I asked him in a staunch voice "What do you want?" He said "Money." I said "Well you ain't gettin' any from me!" I haven't heard from him since. One caller - I told him I was his cousin Farouk. Asked him "How the hell are you doin'?" Obviously I pizzed him off. He said "I'm doin' good - - - mother fµcker!" Then he smartly hung up. Cheezed another when I told him Ganesh was going to punish him for scamming people.

As far as the three tones go - it may be a trigger that activates the "Sorry, this number is not in service at this time" message. But if you don't have the pre-recorded message and a way of activating it - I don't think you're going to be able to use those tones.
 

SamR

Joined Mar 19, 2019
3,391
discourage the constant barrage of scam callers.
All I had to do was call the local private phone company and they installed a filter. Now, if you call the house you get a recorded message that this number does not accept unsolicited calls and to press 1 to continue. Immediately ceased! Now if they only did that for my cell phone. Only downside is you cannot receive any auto-generated robo voice calls with security codes or such. Also auto robo dialed notices of upcoming appointment reminders.
 

Reloadron

Joined Jan 15, 2015
5,934
THANKS to those who provided the frequencies. Since this will be generated by simple CMOS logic using some dividers off a crystal, and not played by a computer or smart phone, the frequencies are what I needed. The wave file will work well with a cell phone, though, for others who want to use it. My intention is to use some presettable down counters from some suitable frequency. So it is going to take a bit of math, which will be tedious but not hard. And the three tones can then be selected by DC control lines. So the final arrangement should be possible for others to duplicate.
Just remember it's about frequency and duration as covered in the link. Pretty wide tolerances.

Ron
 

BobaMosfet

Joined Jul 1, 2009
1,767
In the US, when I dial an inactive phone number, get a loud three tone sequence followed by an announcement that "this number is not in service". The tones do not seem to match the touch-tone frequencies.
I want to try using those tones to discourage the constant barrage of scam callers. Maybe if their computer gets that message they will take me off the list. At least is seems like it is worth trying.
So does anybody know what those tone frequencies are? If I create a circuit to generate that sequence I will share it with everybody.
This is an 'in band call progres tone' called a SIT (Special Information Tone) if you mean the 3 rising tones, usually preceding an announcement describing a problem.

You can go here to see the ITU and Bellcore frequencies/durations etc;

https://en.wikipedia.org/wiki/Special_information_tone
 

Reloadron

Joined Jan 15, 2015
5,934
In the US we have the Federal No Call List, which is totally useless. Completely ignored and rarely prosecuted.
Don't even get me started on that. The NSA can find a single mad cow on the face of the planet but the US Government can't seem to stop annoying phone calls or identity theft. Go figure? Looking at caller ID unless I know the caller I don't bother answering. They can leave a message.

Ron
 
Top