Decades ago, an American company called DAK used to sell a box that picked up on an incoming call (land line, pre-cellular era) and played a short message, usua

Decades ago, an American company called DAK used to sell a box that picked up on an incoming call (land line, pre-cellular era) and played a short message, usually something like "Please enter your extension number" or "enter security code." If the correct code was not entered, it simply hung up. No ring, no answering machine, no hassle. The nice thing was, you could pass your phone number out to everyone, but it would only ring for the people you gave the code to. And it was easy to manage, just give your number as "555-1212 ext.382" or whatever. And if the code got spread too widely, you could just change it and give anyone you wanted to hear from the new code. I keep hoping someone will make an app like that for cellular phones, but most people seem to like saving their spam calls in their voicemail boxes to review them later.