Original blue line copy of the Pong schematic originally drawn by Allan Alcorn, one page, 34 x 22, identified in the lower corner, "Pong, Al Alcorn," with a listing of descending revision dates: "Jan 15, '73 to 'E,' Oct 16, '72, Sept 1, '72, Aug 11, '72." Major sections of the schematic—areas of the circuit responsible for video generation—are labeled "Horizontal Sync," "Horizontal Position," "Vertical Sync," and "Vertical Position," while some other noteworthy areas are marked: "Score Sound Timer," "Hit Sound," and "Coin Switch." Notes in the lower left state: "1. All resistors are 1/4 W Carbon and are 1K unless otherwise stated, 2. All JK flip flops are 74107, 3. All D flip flops are 7474." Folded and in fine condition, with light toning along the folds. Accompanied by a letter of provenance signed by Alcorn, discussing his history as Atari's first hired employee and the story behind his creation of Pong; he used this schematic to troubleshoot problems during the production of Pong arcade games.
Unlike modern video games that use microprocessors and software, Pong was developed using entirely hard-wired transistor-transistor logic (TTL), utilizing logic gates, flip flops, and counters to create a simple interactive game. Alcorn's clever, innovative circuit has been widely studied and earned the praise of electrical engineers and video game enthusiasts alike. Like the game itself, the circuit's elegant simplicity breaks things down to their component parts and uses some clever tricks to create the memorable Pong experience: prominent score counters at the top, segmented paddles that allow a player to put 'English' on the ball, variable ball velocity, and interactive gameplay sounds.
When Alcorn had finished creating the gameplay circuit, he was already over budget but had not yet created the sounds. Atari co-founders Nolan Bushnell and Ted Dabney insisted that they were essential. Alcorn recalls: Nolan said, "I want to have the sound cheering people when you make a score." And Ted said, "I want it to have boos and hisses." Instead of adding new components for sound, Alcorn realized that he could tap into the existing sync generator to make three tones: a low-pitched thunk when the ball bounces off the side walls, a higher-pitched blip when it hits a paddle, and a lower bleep when a point is scored. These sounds added a layer of immersion for Pong players. More importantly, though, they served as an advertisement for Pong in its context as an arcade cabinet deployed into the American barroom: other patrons, intrigued by the novel noises, sought out their source. Soon, they were lining up to play.
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