In probably 1976 for $1 I bought a one-page schematic for such a thing, from classified ad in the back of a magazine. I suppose it was a related version, but II

In probably 1976 for $1 I bought a one-page schematic for such a thing, from classified ad in the back of a magazine. I suppose it was a related version, but IIRC it relied upon 74123 style monostables.