Yes but I’m sure you need at least 5 different Volts for it to work.

Only 1. Standard 70s tech.

OP’s purpose was video security, not doorbells. People pushing the button instead of knocking was an unintentional consequence.

Your 70s doorbell is not helpful.

My doorbell is a sign that says “Knock”, because my 70’s doorbell is broken. It requires 0 cloud services to fix the problem of people pressing an unhelpful button.

[EDIT] To people downvoting this, did you read the article? Specifically, this part:

“Before we had the doorbell, people just knocked on the front door. But now, people would notice the doorbell and ring it instead. This would send a notification to our phones, and then it would also helpfully play a sound on the doorbell itself… outside the door… which we could not hear.”

He then goes on a tech bodgeathon to fix the button, instead of just placing a sing that says “Knock” to go back to the thing that worked before.

Yes but the camera is the crucial bit for the OP, the doorbell is an unnecessary encumbrance.