Digraph

https://craphound.com/spamsolutions.txt

Comfort noise - Wikipediahttps://en.wikipedia.org/wiki/Comfort_noise

Eliminating Robocalls | Hacker Newshttps://news.ycombinator.com/item?id=19424428

https://www.usatoday.com/story/news/2018/11/15/robocalls-verification-system-ftc-fcc-telecommunications-caller-id-shaken-stir/1682591002/

Manufacturing the Librem 5 USA Phone in the United States of America – Purismhttps://puri.sm/posts/manufacturing-the-librem-5-usa-phone-in-the-united-states-of-america/

Mother Earth Mother Board | WIREDhttps://www.wired.com/1996/12/ffglass/

Robocallers “evolved” to sidestep new call blocking rules, AGs tell FCC | Ars Technicahttps://arstechnica.com/tech-policy/2018/10/robocallers-evolved-to-sidestep-new-call-blocking-rules-ags-tell-fcc/

STIR and SHAKEN Overviewhttps://transnexus.com/whitepapers/stir-and-shaken-overview/

The Robocall Crisis Will Never Be Totally Fixed | WIREDhttps://www.wired.com/story/robocalls-spam-fix-stir-shaken/

Your Phone, Your Call - Part I - Eliminating Robocalls - Twiliohttps://www.twilio.com/blog/your-phone-your-call-eliminating-robocalls