Apple Desktop Bus

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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Superseded	RS-422/6522 keyboard and mouse
Superseded by	USB and FireWire (1998–1999)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.