[rootusrootus]

> purely mechanical doorbells

And very elaborate, too! Mechanical doorbells are pretty common here (old city, by US standards, on the west coast), but they are just a handle on the front of the door with a rod that goes through it to a bell on the inside.

[zvr]

Each house has a completely different design on its doorbell: when you come home in the middle of the night (and/or you're drunk), you can recognize your house among every other similar house on the row only by touch.