I have heard, but have trouble finding references to it, that you can build a simple arbitrary waveform generator circuit by using an analog scope, a photodiode, and a cardboard cutout.
You make a photodiode circuit that rails high with no light, but light on the photodiode pushes the signal low. Then you aim this at the phosphor screen with a cardboard cutout of the desired waveform: signal goes up until the phosphor trace is above the screen, and then it gets pushed low (i.e., feedback keeps the trace right on the edge of the cardboard).
Never seen it in action, but I choose to believe it works beautifully :)


















https://en.wikipedia.org/wiki/Teledildonics