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We've all been driven to madness by one form of scammy telemarketer or another for years now. Seems like there's nothing we can do to avoid them.


For your mobile phone, there are apps that can warn you by showing "possible telemarketer" when your phone rings. I've always laughed at that. Why show that warning at all? Who among us will think "Hmmm... The phone says it might be a telemarketer. But hey, I'll answer anyway!" Um... No.

The FCC's Do Not Call list is a joke. I'm enrolled but it hasn't appeared to slow down the deluge of junk calls I get. The phone companies, wireless carriers, and congress obviously don't care or else they'd have done something long ago. e.g. Congress could pass legislation that mandated effective call blockers which would win widespread accolades. But they don't.

robot holding phone receiver

Caller ID-based blocking

Caller ID as a way to identify telemarketers and robodialers is useless. It can be spoofed easily and usually is these days. I could place a phone call and make any name and number I want appear on your caller ID. So any robodialing warning product that relies on the authenticity of the calling number is dead on arrival. Only the most dim-witted telemarketers and robocallers are blocked this way.

Robocall blocking products such as RoboKiller, Nomorobo, Hiya, TrueCaller, and others mostly rely on various incarnations of blacklisting -- that is, blocking/flagging calls from suspected phone numbers. Blacklist incarnations include community blacklists (informed by the collective users of that system), global blacklists (lists shared between products), realtime blacklists (numbers added/removed as robocallers spoof then stop spoofing a certain number), affinity numbers (numbers that match your area code and maybe the first three digits). But each of these approaches have the same intrinsic weakness which is reliance on caller ID.

Because caller ID-based detection is so bad, most products don't dump the call but rather warn you that it may be junk. As I stated up top, who the hell wants that? To me, 90% of a junk caller's aggravation is the intruding interruption of my phone ringing. My phone is not a sales tool for the convenience of telemarketers. Any such call is an unacceptable use of my time and resources.

That's not too unreasonable, is it?

What if you could install an app on your mobile phone that really works and eliminates the unwanted junk phone calls you receive? No warnings and no ringing. Robocallers are hung-up on without you ever knowing except that your phone will be curiously quieter than it used to be.


Because I'm such a language pedant, let us define some terms here:

  • A "robocaller" uses an automated dialer to place the call. When you answer, the calling computer begins playing its prerecorded message. That's when you hang-up, mumble a curse, then go on about your business.

  • A "robodialer" is similar, but all it does is dial phone numbers. When you answer, the call is routed to the next available closer,  who takes over the call. That's the tell-tale pause you experience after answering but before you hear anything.

Robodialers are huge time savers for an operation with (live) closers because the closer doesn't have to manually dial, wait for an answer, and likely get your voicemail. That's unproductive time. The call dialed automatically then is passed to the closer only if the mark (that's you, heh heh) answers and the robodialer detects that it's a human -- usually because humans say "hello" and quietly wait. Most robodialers know if your voicemail answers and will hang up rather than pass the call to a closer, wasting their valuable time.

My method is 100% effective against robocallers and nearly so against robodialers as well.

Prove Thyself Worthy

"Challenge/Response" is a simple type of Reverse Turing Test (wut??) whereby a machine (a computer program) tries to figure out if it's communicating with a human or another machine. In this case, the "challenge" is issued by the machine (my robocaller killer) and the "response" is provided by the party being tested (the party calling you). A machine (robodialer) calling you will fail this test but a human calling you can easily pass it.

You actually see lots of challenge/response systems today! Whenever you see a CAPTCHA*, you know, those things where you have to decipher a string of warped letters with squiggly lines or click on all the pictures that include a cat, well, that's a challenge/response system at work, trying to figure out if you're human or not. Web sites, especially sign-up screens, use CAPTCHAs to avoid automated abuse. Much like what we'd like to use to avoid robocallers, if only we could. Weeeeeeell, it turns out we can.

* CAPTCHA : Completely Automated Public Turing test to tell Computers and Humans Apart.

Challenge/Response works remarkably well at separating humans from machines because the good ones are easy and fast for people to follow but very difficult for a computer to follow. That's the entire point and is basically what I did to eliminate robocallers.

My Robocall Blocker

I set up an Auto Attendant (a computer program) on my mobile phone as a dead simple CAPTCHA. It answers all my calls without ringing my phone and says to the caller "This is Robert's robodial call screener. Please touch 3 at any time to ring through." If the caller is human (and understands English) then easy peasy. They touch 3 then my phone rings as normal -- and the caller hears ringing, too. If I cannot answer, the call is passed to a regular voicemail greeting. If the caller is a machine (a robodialer) then it won't understand my "touch 3" message so my auto attendant simply hangs up and I'm not alerted. Sweeeeeet silence.

What makes this so elegant and superior is its simplicity for the caller. They don't have to announce themselves, as if requesting an audience with the pope, as some call screening systems require and I'm not presenting them with an aggravating-as-hell endless list of options like you hear when calling most large companies. And since everyone can get behind an effort to reduce robocalls then callers should not mind the simple "touch 3" request. Next time they call, they'll already know to touch 3 and can do so right away.

Potential Downsides

Unfortunately, the tools I'm using don't allow me to whitelist callers on my contacts. Everyone hears the "touch 3" message no matter who they are. But that's a tiny price to pay, in my opinion, to avoid a ton of robocallers.


If you rely on certain legitimate automated callers to give you info, like maybe your kid's school is cancelled due to weather, your prescription meds are ready to pick up, or some such, this system will interfere with that. Those legitimate info-only robocalling systems cannot understand the "touch 3" message so they'll never be able to ring through to you.

But I don't think this is a big problem these days. Most legit organizations that need to reach you or broadcast an important message can be configured to send a text message, which this blocking system doesn't touch. The days of voice-based info announcements are waning, thankfully. Text messages are the best way to receive such notices anyway.

How do I set it up?

There's a number of steps to setting this system up and may be a bit over the top for some non-geeks. There's also an ongoing cost which is pretty modest -- about $15/month using the service that I'm using (Line2). To me, that's a small price to pay for a very-nearly 100% effective robocall blocker considering that in one month I might receive a hundred robocalls.

It's beyond the scope of this page to explain every step in detail but broadly speaking, here's what happens when someone calls me.

  • My mobile immediately forwards all incoming calls to a virtual VOIP number hosted by "Line2". No local ringing.

  • On Line2, my Auto Attendant (AA) answers and plays the "touch 3" message then waits a few seconds

  • If the caller touches 3, then proceed below. If not, my AA hangs up and that's it.

  • Caller is forwarded to the Line2 app on my mobile phone. It rings. I see the caller ID or contact name as normal.

  • If I answer, then we talk. Then hang up when I'm done. Nothing different there.

  • If I don't answer, the call is routed to a Line2-based voicemail that plays my greeting, like any regular voicemail.

Want to hear this in action? Give me call at my old Florida number 561.818.1716 and hear it for yourself. I'll never know you called unless you touch 3. If you do touch 3 then please be polite and don't hang up :-) I'll answer if I'm available.

As I stated above, the only thing different that a caller encounters using this system is the brief "touch 3" message. That's it. And since I can be more confident that a ring-through is a real human, even from numbers marked "unknown", then I'll answer. And my blood pressure doesn't go up!

Telemarketer Bypass? It's possible that a live operator (robodialer hand-off) may also touch 3, but I'm not too concerned. It's also possible that a real person is actually dialing the phone, like in the old days. But that's pretty rare today. Most junk callers use robocallers that play a prerecorded message. Closer hand-offs, if any, probably come at the end or if I would touch a key for more info (which of course I never do). Secondly, most robodialers dump a call that is answered by a non-human (like my Auto Attendant) especially if the robodialer was designed to hand off the call to a closer.

If you don't mind paying a few bucks a month to pretty much eliminate junk calls then you might like this solution. If you want me to set up something like this for you, then give me a call (or text or email). My contact info is on the home page.

March 2021 Update

There's a landline cordless phone system that can do the same thing. VTECH makes a cordless phone system that includes a call blocking feature that works similar to above but without any monthly subscription. Callers to your landline are quietly answered by the base station and asked to touch # to ring through. If the caller doesn't touch # then the call is dropped -- all without disruptive ringing.

Here's a link to

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