From whence cometh the blackboard background maths?

It reminds me of about 1971 when I was offered the opportunity to design the cover of a report, study or somesuch, on a digital satellite.

I thought it would be a good idea to make the background a portion of a digital circuit. But, could I find a schematic to suit that wasn't classified? It was difficult, but I got there in the end.

Just for fun, I've recreated something like the original cover

The cover was background darkish blue, and the circuit was, as I remember, white fine lines, subdued.

I have been trying to reproduce the exact effect, but I can't see how to get a thin clean white line diagram on top of a blue background field. One problem is that I can't find a digital circuit diagram with the sort of components available back in the day. I've searched for digital schematic diagrams in my browser, and there are many different sorts of diagrams there. But not quite with the number of small IC's used then, in the absence of complex computer and other multifunctional chips. So the diagrams are of low resolution and don't lend themselves to much processing.

To get the cover  background image, I had to do this.

1) Find a black on white circuit diagram, and crop a portion with sufficient quality in the lines to invert. This was my initial problem, as I couldn't find a nice complex circuit diagram with heavy enough lines,  as I was copying from one of those image browsing fields  you get in a search result.

2) process the image in photolab (out of PPX9) from B/W to get blue lines on a white background

3) Process the image by inversion to get yellow lines lines on black and then on to white lines on blue.

4) For this image, rotate and crop irregularly to fit image to A4 page.

The original, back in the day, was implemented by the company print room.