Dealing with Robo calls - phone ring suppressor

We use CallClerk to help control robo calls. It has a white list and a black list - white list callers are let through, black list ones are dropped and all others are put through to CallClerk's answering machine.

So, our incoming calls are being pretty well managed. There is still an annoying bit, though. Black list callers and don't-knows still cause the phones to ring once or twice before CallClerk answers. "What's the big deal?" you say? The big deal for me is that it interrupts whatever I'm doing. I cannot ignore a ringing phone, even if I won't have to answer it. When the phone rings, it gets my attention while I wait to see if it will stop after 2 rings or if it's going to keep ringing and I'll want to answer.

This post is about a simple little circuit that suppresses those annoying initial 2 rings. Now, if the phone rings at all, it is a known caller and I should see who it is.

We have Vonage phone service, which uses a modem attached to the internet through our router. Its output is a 2-wire POTS-standard phone line. That line has 50v DC in standby and superimposes 20Hz 70v RMS for ringing. My circuit detects the AC and counts rings. For the 1st 2 it uses a relay to disconnect downstream phones from the line. The breadboard version works and before I build it for real, I'd like your comments/constructive criticism.

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The left side is the ring detector and the optocoupler puts out a pulse for each ring signal cycle. The 12v zener screens out low voltage voice and dial signals. (The 10k resistor on the optocoupler emitter was picked out of the air & I'd welcome suggestions for a better value.)

The 55ms "ring" one-shot spans one 20Hz cycle. It is re-triggerable and provides a continuous signal for the duration of a ring. It provides a single edge for clocking/shifting the counter.

The counter is a shift register whose bit 3 signals the end of ring suppression. The shift register has the advantage over a counter in that no decoding of state is required and there's no overflow.

The 6s one-shot spans the interval between rings. It is re-triggerable and is true for the duration of ringing. Its time out is used to reset the shift register. The 6s one shot triggers on the leading edge of the ring pulse and the 55ms one on the trailing edge. This is to prevent a race on the clock and reset shift register inputs.

The relay is picked only during the ring and not during the inter-ring period. This allows the caller-id signal after the 1st ring. I didn't think that the phones would see the caller-id without a ring signal preceding it, but they do.

The main parts are: Optocoupler: FOD817

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One shots: CD14538B
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Shift register: CD4015B
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Relay: G6K-2P
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MOSFET's: TP2104
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VN2106
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Thanks in advance, Bob

PS - We had been getting a very annoying number of robo calls and by some bizarre coincidence our robo calls have stopped almost entirely since I hooked up the circuit (even though they don't ring, I check the Vonage log for them).

Reply to
Bob Engelhardt
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Please note that Panasonic has this feature in some of the phones as part of the "call block" feature: If you do not want the first ring from a number on the call block list to sound, turn the "first ring setting" to "Off". The default setting is "On".

Some of my customers use NoMoRobo service (usually via Comcast): Notice that it has an adjustable number of rings before passing the ringing to the phone. Most seem have it set to 1 ring delay. My guess(tm) is that CallClerk might be a bit slow to respond. Looks like the software only allows suppressing one ring: Perhaps you should request that CallClerk add a variable number of rings setting (as in NoMoRobo) before embarking on a hardware solution?

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Reply to
Jeff Liebermann

Thanks for the response, even if it wasn't what I asked about .

The Panasonic feature is a good one, but its weakness is that caller-id spoofing makes block lists very ineffective.

NoMoRoBo and CallClerk sit ON the line, not IN it. So, they can't do anything until the 1st ring has happened and they get the caller id. One ring is enough to interrupt whatever I'm doing.

The only real solution to this is caller authentication and phone service providers doing the blocking before a ring is even sent out. Until/if then, I'll suppress the rings and my callers will have to get used to the idea that I'm not ever going to pick up until the 3rd ring.

Bob

Reply to
Bob Engelhardt

Have you built a circuit like this? I don't know what electronic phones wi ll do with the initial ring impulse that will make it through your design. Maybe it won't be big enough to trigger anything. I don't know enough of the details of the phone line to know if the ring detector will see the rin g faster than the ring circuit in the phone. An 8 pin MCU will give you mu ch more flexibility in the event this circuit causes chirping of the ringer in the phones. I know people like the ease of not dealing with software, but it can be so much more useful. I guess with a relay you aren't going t o power it from the phone line?

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Reply to
gnuarm.deletethisbit

I have built it and it works very well. There is only a 1/2 cycle of ring on the line & 3 different electronic phones do not react to it. The thing about an MCU is the learning curve, however, there's not anything more that I would have the circuit do. And it would only replace the one shots and shift register. I have a 12v wall wart for power.

Reply to
Bob Engelhardt

s will do with the initial ring impulse that will make it through your desi gn. Maybe it won't be big enough to trigger anything. I don't know enough of the details of the phone line to know if the ring detector will see the ring faster than the ring circuit in the phone. An 8 pin MCU will give yo u much more flexibility in the event this circuit causes chirping of the ri nger in the phones. I know people like the ease of not dealing with softwa re, but it can be so much more useful. I guess with a relay you aren't goi ng to power it from the phone line?

er.

Yeah, good. I seem to remember years ago having a phone that would trigger a ring blip on various noise conditions.

I guess you can tuck the circuit away someplace, but it would likely be wit hin earshot in my place and I'd hear that relay clicking each time the phon e line tripped it. I think I'd go with a programmable device and a pair of solid state relays. Then it could be phone line powered and I'd never kno w it was operating.

But then I gave up my land line years ago and my internet phone is my cell phone. Works great and does a pretty good job of screening calls without b uilding any hardware.

So Call Clerk is a device? I haven't seen those. It's pretty bad when the re are so many people calling to annoy you that a machine is required to pr event their calls. When I'm in my car I like to answer the calls and tell them, "Yes, I'd love to lower my credit card interest rate!" They eventual ly figure out I'm scamming them and they hang up, sometimes with a rude rem ark. That's how I know I won!

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Reply to
gnuarm.deletethisbit

Well, at least YOU did not get bombarded with 12 (yes,,a real dozen) calls in less than 5 minutes from the same caller (caller id ="not available", number = "1009"). I left out the other 12-14 calls to me BEFORE this barrage.

So i had my landline number changed. PITA informing all of my credit card providers and banks etc.. Should be a way of automatically passing these changes on..

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Reply to
Robert Baer

Perfectly acceptable... In the UK we have a similar thing but it is handled at the exchange and we don't get any ring for blacklist numbers. 'New' callers have to announce who they are and that voicemail is passed to me as a ring tone... If I want to accept the call, I press 1, else press 3 to black list... works well.

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Reply to
TTman

On 4/24/2019 5:41 PM, snipped-for-privacy@gmail.com wrote: ...

Yes and no. It is PC software that uses a USB voice modem ... like you'd use if you have dial-up internet. The modem allows CallClerk to look at the line, but also to send an outgoing message for its answering machine.

Reply to
Bob Engelhardt

That sounds the perfect solution. If only the US would adopt it. (I remember when the US phone system was the envy of the world. When even some European countries had such limited systems that there were phone offices that one could go into to make calls.)

Reply to
Bob Engelhardt

So does the Call Clerk sit between the house phones and the phone line? If so, you can put the ring suppressor between the Call Clerk and the phones and not worry with passing the CID info, not that it does much for your des ign, eliminate one transistor.

Seems there should be a way to do this in the Call Clerk and not need a sep arate box to suppress the rings. I guess the only way the modem can suppre ss the rings is to go off hook which would prevent receiving the CID.

I'm not sure how the modem relays are designed. I assume they use one rela y to go off hook and to disconnect the line to the telephones.

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Reply to
gnuarm.deletethisbit

They could add that, but it would cost extra just as CID and all the other features used to. But I thought you didn't have a land line, rather it was an Internet phone, no? So it doesn't really have anything to do with the phone service.

Have you asked Vonage about providing a service like this? That's the best solution.

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Reply to
gnuarm.deletethisbit

The CallClerk modem sits on the line, like a phone. I.e., in parallel, not series. So, it can't interrupt except by picking up and it only does that after the 1st ring and it has seen the CID.

Reply to
Bob Engelhardt

Internet phones, e.g. Vonage, are really no different than landlines. They could all provide the same blocking that the UK has. But it would require caller authentication, without which CID spoofing renders central blocking useless, or nearly so.

Reply to
Bob Engelhardt

...

separate box to suppress the rings. I guess the only way the modem can su ppress the rings is to go off hook which would prevent receiving the CID.

There's the problem. The modem has a passthrough jack that potentially cou ld be used to block rings with. The standard way of wiring is to pass ever ything through until the modem goes off hook, then disconnect the passthrou gh phone jack. If the internal connection of the off hook circuitry allows it could be used to disconnect the phones from the line during the first t wo rings.

My point is this whole thing is a bit of a bodge. The Vonage unit should d o all this. So you add a PC running the CallClerk to handle the spam calls , but it still rings the durn phones. So add a two ring canceling custom d esigned circuit... Isn't there a children's song like that, about swallowi ng a fly?

Vonage should be handling all this the same way my cell phone does, just do n't ring the phone unless it is someone on my white list.

Have you thought of using a cell phone? Is Vonage any cheaper than a cell? I think my cell bill is only $27 a month if I wasn't paying for the phone in installments and that includes my data usage. The phone works through the internet when I am at home or anywhere it can get on the Internet. It uses cell towers otherwise. It provides a similar screening service to wha t you describe, but works without ringing the phone. The calls from number s on the black list don't even show up. How is Vonage better than that? T he cell phone also gives you all manner of Internet connectivity.

One thing I've noticed is that many spammers change numbers at will. So bl ack lists don't work well. I had one guy call me today and I put him on ho ld to get rid of him. He called back and it was a different number. I act ed like I couldn't hear him and he was swearing at me, lol. On the off cha nce I really couldn't hear him he called a third time and it was a third nu mber. I should have responded and put him on hold again. LOL!

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Reply to
gnuarm.deletethisbit

On 4/25/2019 9:53 PM, snipped-for-privacy@gmail.com wrote: ...

"Should" - of course ... that doesn't mean that they will.

The problem with white-list only is that there are some callers that aren't on the white list that we don't want to kill. E.g., the hospital that calls back from a different number, the town clerk that we never thought to put on the white list, etc. CallClerk takes their message.

Reply to
Bob Engelhardt

Yeah, a cell phone will do the same thing.

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Reply to
gnuarm.deletethisbit

I us nomorobo and a Panasonic phone that can (and does) block the first ring. This is an effective combination for blocking most crap calls. the ones with the spoofed caller ID still sometimes get through though.

Reply to
rangerssuck

Don't they all "spoof" caller ID? I think I posted about getting three calls from the same guy in 10 minutes and they all showed different numbers.

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Reply to
gnuarm.deletethisbit

Many do spoof the ID, but there are probably 25 times a day that I see the phone screen light up (meaning that there's an incoming call), but no ring, meaning the call was terminated - usually by nomorobo - before the second ring. Not perfect, but better than nothing.

Reply to
rangerssuck

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