Apple Desktop Bus

Apple Desktop Bus
The Apple Desktop Bus icon and an early Apple Desktop Bus keyboard
Type Human input device interface
Production history
Designer Apple Computer
Designed 1986; 38 years ago (1986)
Manufacturer Apple Computer Inc.
Produced 1986 to 1999
Superseded RS-422/6522 keyboard and mouse
Superseded by USB and FireWire (1998–1999)
General specifications
Hot pluggable occasional support
External yes
Pins 4
Connector Mini-DIN
Data
Data signal Bi-directional serial command stream
Bitrate 125 kbit/s maximum
(~10 kbit/s actual)
Max. devices 16 maximum
(~5 actual, 3 supported)
Protocol Serial
Pinout
Female socket from the front
Pin 1 Apple Device Bus Data
Pin 2 PSW Power on
Pin 3 +5 V +5 volts power
Pin 4 GND Ground
Same connector as S-Video

Apple Desktop Bus (ADB) is a proprietary[1] bit-serial peripheral bus connecting low-speed devices to computers. It was introduced on the Apple IIGS in 1986 as a way to support low-cost devices like keyboards and mice, enabling them to be connected together in a daisy chain without the need for hubs or other devices. Apple Desktop Bus was quickly introduced on later Macintosh models, on later models of NeXT computers, and saw some other third-party use as well. Like the similar PS/2 connector used in many PC-compatibles at the time, Apple Desktop Bus was rapidly replaced by USB as that system became popular in the late 1990s; the last external Apple Desktop Bus port on an Apple product was in 1999, though it remained as an internal-only bus on some Mac models into the 2000s.