Oscilloscope signal mixer from 1939

[Shock]

If you haven't seen Mr Carlson's lab channel from the list of electronics related youtube channels yet I highly recommend it. This video is about as good as it gets (no repetitive fluff or hype) for fans of repair and restoration. Looks like he might be almost able to become a full time youtuber as his patreon supporters are up to $4,000 a month and halfway to his $8,000 a month goal.

[Vgkid]

I watched that one last night. I found it very interesting.