Apple Desktop Bus connection utilises the Mini DIN-4 connector, which, oddly, is also used by S-Video, and the pinouts are actually interchangable. ADB provides power and I/O to compliant devices, usually limited to keyboard & mouse. Warning: never connect/disconnect an ADB device while the system is powered on. You have a 1/10 chance of permanently killing your ADB controller silicon. Obsoleted by Apple Computer in 1998, in favour of USB and later FireWire.