They ended up with all electronic contacts when they switched lens mounts for the “eos” series cameras though at the expense of not having backward compatable lenses. (I had a bunch of manual focus lenses at the time…) They had one “auto focus” camera for the old lenses the t80. (https://global.canon/en/c-museum/product/film115.html) but almost no lenses supported autofocus.

I think most of settings the camera sent to the older lenses (aperture primarily) was done mechanically.

The way these old cameras autofocused was pretty interesting. With some light passing through a semi transparent mirror onto different sensors.

Edit: this site has another page about autofocus. Quite extensive.

https://exclusivearchitecture.com/03-technical-articles-DSLR...

Shorter canon article: https://support.usa.canon.com/kb/s/article/ART170280

I have one of those mirrorless slrs now. The focus is amazingly good. Lots of software (eye detect etc). The focus sensors are integrated into the image sensor I believe.