So draw the block diagram of something you worked on in school. Or, I don't know, a radio or something, if you're a hardware person.

Someone who answers, "I can't draw anything for you because everything I know about is somebody's private IP," isn't going to get the job. At least, not if I'm doing the interviewing.

You must know something about something else. Right?

Or just interview some place that doesn't give this kind of interview, like most companies. It's pretty trivial to get hired even if you can't talk about technical specifics along the lines of an architecture diagram.

Sure, I'd like to draw a vaccum cleaner, because this interview seems to suck and be unrelated to my job role. :)

"Great, that'll do nicely. What can you tell me about how a vacuum cleaner is built and/or how it works? Also, vacuum cleaners are pretty old tech. Is there room for further innovation in that area? If so, what angles would you explore if you worked at a vacuum cleaner company?"

This is a great way to get BS'd into thinking someone is qualified when they're not. Work sample tests are all you need.

"Awesome, then you've got nothing to worry about!"

Thanks, I can start on Monday

This is why this question is so informative. There are a ton of people in this thread arguing that they can’t describe any technologies they understand because of NDAs.