The I-PAC (Interface for Pc to Arcade Controls) are a range of boards which allow connection of arcade controls such as buttons and joysticks to a keyboard port or USB port on a PC motherboard. It was designed around the MAME emulator which supports over 1000 arcade games and can be used with other emulators or any software which requires keyboard or game controller input. 
It is designed to be used inside an Arcade Games cabinet with the PC motherboard also mounted inside, but could just as easily be used with simply a control panel without a cabinet. 
Special shift function buttons mean that a normal keyboard is only be needed for game loading and configuration, not for gameplay. All key codes can be programmed but you dont have to as you can use the built-in default configuration which has all standard MAME codes for quick and easy installation. Programmed keys codes are stored even after power off. 
The I-PAC2 has 32 inputs. They are all programmable and are marked as 2 joysticks, 8 buttons each, plus coin1, coin2, start1, start2 and Mame control keys. Any inputs can be assigned as a shift key to access an alternate code set. This board also has a connector which can be configured to plug our trackball and spinner into, or for our console interfaces.
The MAME control keys are by default assigned to the "A" and "B" inputs. Check out the code table here for all default assignments.
The I-PAC4 has 56 inputs. All programmable and marked as 4 joysticks, 8 buttons each plus coin 1,2,3,4 and start 1,2,3,4. Any inputs can be assigned as a shift key to access separate codes sets.

• Connect very simple your joysticks and push through this interface.
• The iPac has its own microprocessor so no ghosting or delays when pressing multiple buttons simultaneously. (up to 6 simultaneously)
• Standard pre-installed program for MAME, adjustable with the iPac software.
• Has a 'shift' function so all the buttons works as another function.
• LED indicates whether the iPac is properly connected to the PC via a PS/ 2 or USB cable.
• The iPac remembers his latest program, even after power off.
• No drivers needed
• Connection for an additional PS / 2 keyboard