I have to agree with the grandparent -- intercoms were quite common in houses in the 60's and 70's. Then they fell out of fashion, possibly because of cordless

I have to agree with the grandparent -- intercoms were quite common in houses in the 60's and 70's. Then they fell out of fashion, possibly because of cordless phones? Most multi-handset cordless phones have a built-in intercom that will ring all the other handsets and establish a loopback call. But I bet not many people even have those any more ... So, I would say this is not so much new as retro. True old-timers would recognize this use case right away.