System 16 is the 56 pin arcade game wiring harness used by many older Sega titles that run on variations of the System 16 hardware. This is a plug and play standard, you simply unplug one gameboard from the edge connector, and then plug in a new one for instant action. But you have to be very careful, you see the System 16 standard and the JAMMA standard both use the same exact 56 pin edge connector. But they are not compatible. Plugging one into the other will more than likely fry your gameboards. So always double check to make sure you know what kind of board you have. If you own boards of both types then you can make a fingerboard that will allow you to use games from one standard in a cabinet wired for a different standard.
Most titles on this platform have a nasty suicide chip encased in a solid block along with the main 68000 CPU chip. It is "game over" permanently when this battery dies. So enjoy your System 16 games now, because they won't be around for much longer.
Some titles can be repaired using bootleg chips and a new CPU, however not all titles can be fixed in this manner, and it is fairly expensive if you are unable to do it yourself.
The System 16 Pinout
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Solder Side | Parts Side
================================|===================================
GND | A | 1 | Ground
----------------------------|---|---|-------------------------------
GND | B | 2 | Ground
----------------------------|---|---|-------------------------------
+5V | C | 3 | +5V
----------------------------|---|---|-------------------------------
+5V | D | 4 | +5V
----------------------------|---|---|-------------------------------
+12V | E | 5 | +12V
----------------------------|---|---|-------------------------------
Counter 2 | F | 6 | Counter 1
----------------------------|---|---|-------------------------------
Key | H | 7 | Key
----------------------------|---|---|-------------------------------
Player2 Button 3 | J | 8 | Player1 Button 3
----------------------------|---|---|-------------------------------
Player2 Button 1 | K | 9 | Player1 Button 1
----------------------------|---|---|-------------------------------
Player2 Button 2 | L | 10| Player1 Button 2
----------------------------|---|---|-------------------------------
| M | 11|
----------------------------|---|---|-------------------------------
Player2 Down | N | 12| Player1 Down
----------------------------|---|---|-------------------------------
Player2 Up | P | 13| Player1 Up
----------------------------|---|---|-------------------------------
Player2 Right | R | 14| Player1 Right
----------------------------|---|---|-------------------------------
Player2 Left | S | 15| Player1 Left
----------------------------|---|---|-------------------------------
| T | 16|
----------------------------|---|---|-------------------------------
| U | 17|
----------------------------|---|---|-------------------------------
| V | 18|
----------------------------|---|---|-------------------------------
| W | 19|
----------------------------|---|---|-------------------------------
Player1 Start | X | 20| Coin 1
----------------------------|---|---|-------------------------------
Player2 Start | Y | 21| Coin 2
----------------------------|---|---|-------------------------------
| Z | 22| Test Switch
----------------------------|---|---|-------------------------------
| a | 23| Service Switch
----------------------------|---|---|-------------------------------
Speaker - | b | 24| Speaker +
----------------------------|---|---|-------------------------------
Vid Green | c | 25| Vid Red
----------------------------|---|---|-------------------------------
Vid Sync | d | 26| Vid Blue
----------------------------|---|---|-------------------------------
Ground | e | 27| Ground
----------------------------|---|---|-------------------------------
Ground | f | 28| Ground
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The following games are known to use the System 16 pinout. There may be others as well. Quartet is a bit of an oddball, as it also has a second connector used for then player 3 and player 4 controls.