Most large condo complexes have some sort of secure entry system. Modern ones tend to have a voice intercom where you can buzz in your visitors via a code on your phone. Sometimes there is also a video camera at the entry gate, but almost none are as groovy as the one I stumbled upon yesterday in a 1985 condo.
When a visitor buzzes from the entry, you pick up this handset to speak to them.
But what if you want to see who’s at the door? Well, just pop open the Jetson’s-style monitor! (That is a mini-CRT that pops out!)