1927 documentary on how to dial a telephone

This charming short film (part documentary, part cartoon) explains how to use a dial telephone:

If you think about it, there are a lot of moving parts to this interface besides just using the dial! You have to know how a telephone directory works; you have to know what a dial tone, a ring, and a busy signal all indicate; plus, you have to know the etiquette and conventions of telephone conversations, all of which requires a certain amount of training. It’s certainly much easier on the user’s side to use an operator to make a telephone connection. But before computers, you can’t do that at scale. Think of all that knowledge and training, now evaporating before a new UI paradigm.