Dual trace build for oscilloscope and cellphones

[Smithdoor]

Here one I found today from Electronic World 1964.

https://www.worldradiohistory.com/Archive-Electronics-World/60s/1964/Electronics-World-1964-02.pdf

 

[Smithdoor]

Here is a online oscilloscope

https://academo.org/demos/virtual-oscilloscope/