This trick works best on CRT analog oscilloscope. The idea is to split a composite video signal into two separate X and Y signals that are fed to an oscilloscope (Tektronix 465m in this particular case). The signal split is performed inside an LM1881 chip that takes NTSC composite video signal and splits it into two sync signals that are fed directly to the scope.
Signal intensity is generated via Z-axis input that is present on the scope. A composite video signal sent to z-axis input. The only problem of the scope video monitor is that the signal gets inverted, so the simple inverting buffer is used for the z-axis. The author encourages us to keep experimenting with video signals instead of copying stuff blindly.