Bill Hammack (engineerguy) has an excellent video on the IBM Selectric titled IBM Selectric Typewriter & its digital to analogue converter.[1]

[1] https://www.youtube.com/watch?v=bRCNenhcvpw

One of the Teletypes I used to work on had an eccentric-driven Wiffletree to position the typebox. This was necessary because of it's high speed[0] to decode the ASCII character set (it wasn't a Baudot machine). The selector cam at the end of the machine would do the serial-to-parallel conversion, then clutches would rotate the eccentrics powering the wiffletree to select the character.

If you look at the ASCII chart [1] you can select a character via binary tree - the Wiffletree being a mechanical equivalent.

[0] For a Teletype

[1] https://en.wikipedia.org/wiki/ASCII#/media/File:USASCII_code...