ADB

Serial port for Apple Macintosh computers.Apple LocalTalk serial interface, and an Apple Desktop Bus (ADB) interface. Starting in 1986 with the Apple IIGS, the company began using ADB (Apple Desktop Bus), a universal serial port that could handle a wide range of daisy-chained input devices, from keyboards to trackballs to graphics tablets, in addition to the two RS-422 serial ports Macs used for printers, modems, and AppleTalk networking. Apple rapidly transitioned to USB and removed ADB and legacy serial ports entirely starting with the 1998 iMac.  While the iMate is not very exciting in itself, it provides an invaluable service to those that need to connect older ADB devices for various reasons. USB to ADB adapter is available for USB equipped Mac