This idea probably isn't original with me, but I haven't seen it described anywhere.
Ralph Baer used a similar design to generate random X/Y locations for a spot displaying on a TV set. This was part of his 1966-67 video game prototype #2. Here, the idea was brought by John Mason, an engineer working in Ralph's division at Sanders Associates (now BAE). He called it the "Cludge Circuit". A partial schematic of the random X/Y generation is included below.
Here's Ralph's description:
Objective: To generate two signals that can randomly vary the position of a line or spot on the screen in H and V; an analog "random number generator.
Operation: Two sets of free running neon-relaxation-oscillators are shown at the top of the schematic. The left hand triplet sums their sawtooth outputs into the lower two-stage amplifier. The frequencies of these three sawtooth shaped signals are all different and are somewhat slower or faster than the field rate (60 Hz). The right hand set works at slightly higher or lower rates than horizontal line rate (15,734 Hz). When these signals are applied to the H and V DMVs of the game circuitry, they cause both H & V position of the displayed symbol (say a "spot") to vary, i.e. to randomly move about the screen By experimentally adjusting the frequencies of the neon oscillators, theses random movements can be made slow or fast. Higher oscillator frequencies cause multiple spots to be displayed at different locations of the screen. The two amplifier outputs are delivered to field-effect transistor emitter followers to the V and H inputs of a spot generator. The unijunction-driven relay at the center of the schematic is a timer circuit which was used in various games played "against time".
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