Dealing with Robo calls - phone ring suppressor

Bob Engelhardt · 2019-04-24T14:29:40+00:00

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. 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 ...

Apr 24, 2019 21 Replies

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krw 7 years ago

At least 95% of the spam calls to my cell phone have spoofed caller ID. They use the same area code as my phone, which is 1200mi from where I live. More than half are insurance calls (making them useless, even if I were stupid enough to buy what they were selling).

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Ingvald44 7 years ago

I have one persistant spoofer that uses MY OWN PHONE NUMBER! I blocked it. Strange.

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