There is a couple of places, where the ball rolls over two metal wires or hits another ball behind a rubber band and that ball connects two wires. On the bottom side of the table the two wires are soldered to cables, that are connected to a keyboard. I basically opened an old keyboard an trashed all the keys. Then i was able to glue pairs of cable to the print plates grid - the place that gets conectet by a key (e.g. "A") to make an input. For this pinball table I connected four or five letters like this to different sets of wires on the table. So "A" would be point input, "w" would be ball out. "r" would be bonus activated, "q" would be coin insert and so on. The keyboard then is connected to a PC, that runs a small Flash app. (Back in the Flash times ahhh :-) The PC also is connected to an old flat screen, that I got for free from my work place. Now the Flash game manages all the input, activates sounds, flashes the graphics, counts and adds up points or sets the game on game over, when all the the three balls have been counted out. At kzfaq.info/get/bejne/qq2KfdiEqbDXc4k.html you can see how I am pressing the coin insert button. At kzfaq.info/get/bejne/qq2KfdiEqbDXc4k.html you can see the ball running down an "aisle" with a pair of wires. The Ball makes the connection and the game app counts the input. At kzfaq.info/get/bejne/qq2KfdiEqbDXc4k.html and forth you can se the ball hit an other ball, which in turn connects two wires. (This whole mechanism is places behind a rubber bumper. At kzfaq.info/get/bejne/qq2KfdiEqbDXc4k.html you can see me hit the bonus track, which is one big connector... :-) At kzfaq.info/get/bejne/qq2KfdiEqbDXc4k.html is a close up of me hitting the other ball counter... Great question by the way. I hope you make something creative and show it to me :-) I guess nowadays you would use an arduino or raspberry pie to make this kind of control...