...software that detects high frequency calling patterns, and answers any robo-generated number calling, and hangs up before people have to deal with it.And the price was right: "Nomorobo costs nothing to install on your landline."
It doesn't block all spam or marketing calls - just the ones that are computer-generated. But we are delighted with the result. In the afternoon and evenings our phone will occasionally ring once. Then stop. And without even the annoyance of a message on the answering machine. I don't know of any downside.
Here's the company's website.