What is Apple Desktop Bus (ADB)?
The Apple Desktop Bus (ADB) is an obsolete, slower serial bus that is used to connect input devices such as a keyboard or mouse to a personal computer (PC). It was mainly used with Macintosh platforms such as the Apple II models. It can store multiple data bits in its register and decode a single digit or address. With the introduction of Apple's iMac in 1998, the ADB was replaced by the Universal Serial Bus (USB). Although ADB devices are still available, most Apple hardware manufacturers have not supported them since 1999.
The ADB is one of the most cost-effective buses in history. It was developed by Stephen Wozniak, the co-founder of Apple Computer Inc. The ADB emerged in the mid-1980s after a month of research and was first implemented with the Apple II GS in 1998.
After the development of the Apple II GS, the ADB was used on all Apple computers, starting with the Macintosh SE and Macintosh II. The ADB was also used on various systems that had a 680 × 0-based microcomputer such as NeXT, Hewlett Packard (HP ) and Sun Microsystems used.
Although the ADB has not been used to connect input devices since it was superseded by USB, it has been used as the internal interface protocol for iBooks and PowerBooks since February 2005.
The ADB uses a four-pin mini-DIN connector with a maximum length of five meters, which can also be used for separate video (S-Video). One pin is used for data, two pins are used for the + 5V power supply, and one pin is for ground. In addition, a power switch or PSW pin is connected to the host computer's power supply, which allows signals for startups to be interpreted from a key on the keyboard rather than relying on ADB software.
The ADB supports up to 16 individual devices with unique addresses. However, due to the potential for signal degradation, it is recommended that only three devices be connected to each ADB.