Well, it's not morse code exactly. It's just the number of flashes for the number you want to dial. 606 = six flashes -stop- ten flashes - stop- six flashes...
What's even more amazing is the POTS switching used to be entirely mechanical.
I was wiring a phone jack in my room years ago and my mother asks why the phone is off the hook (and good thing she didn't put it back on either). Well that's 48V on the line there when it rings, that will do some damage.
Like so many other people she was shocked there was so much on the line, I have no idea why I am amazed people don't understand the world/technology around them.
When I was a kid my parents didn't want me to have a phone in the bedroom for various reasons, and eventually their bedroom phone broke such that some of the numbers wouldn't dial, so they gave me that one so I could answer the phone when it rang.
I very quickly figured out the manual pulse-dialing trick.
Their reasons for not wanting me to have a phone in my room came to pass.
cool trick: car batteries only have 3 more volts than a 9v battery. the next time your car battery dies, connect a jumper cables to your tongue to see if it's dead!
since, as everyone knows, voltage is the same thing as current