The posts re the problems to do with logging into NAT, and now the "Are you human?" reminded me of early days of electronics.

When our son was at university - he's now 50 yrs old  - so roughly 30 yrs ago.

Uni lodgings had installed phones in every room, instead of a 'community phone' where who ever answered had to try tracking the needed student down -  usually unsuccessful!

If I rang my son, it went like this, Ring the lodgings number, let an answering system drop in, then enter another three or four numbers for the particular room.  The system could also be used as a room to room convenience call system.

My son - studying electronic engineering - and his mates 'wondered' how many room to room calls the system could take.

So they  [ over the evening meal] devised a scheme - everyone to start ringing others, and see what happened!  The inevitable - system overloaded!  System quit.!

They thought it was a great joke, and Jamie [son] was telling me.

My reaction "What would happen if some parent had some emergency, and needed to contact son or daughter urgently, while you smart minds had the system out of action?"

"OH !  we didn't think of that!"

Like I said -  30 years ago. Mobile  [or cell] phones now, so no problem.