ranger@ecsvax.UUCP (Rick N. Fincher) (05/07/87)
Apple Desktop Bus: Possible length The Apple Desktop Bus, or ADB, is available on the Apple IIGS, Macintosh SE and Macintosh II for connecting keyboards, mice and other input devices to the system. The Apple Desktop Bus protocol will accomodate up to 16 devices. ADB devices are typically daisy-chainged together. Some devices may contain enough internal resistance to limit the number of devices you can connect. For instance, a maximum of 4 Apple Keyboards or Apple Extended Keyboards plus 1 mouse may be daisy-chained together before increases in DC resistance result in drops below TTY levels. It is possible to connect 5 Apple IIGS ADB keyboards and a mouse together before resistance increases to where input via some devices will be "lost". Look out for other ADB devices that may have similar traits. If input isn't reaching the CPU, break the chain into two chains (supported by 2 ADB ports on the Macintosh SE and Macintosh II). An Apple IIGS has only one ADB port, so if input isn't reaching the CPU, power off the GS, connect the particular ADB input device or devices you wish to use, then connect a limited number of other ADB devices, power up, and try again. Alternatively, "Y" connectors could help create additional chains and reduce the number of devices on any one of the those chains. Apple Technical Communications