I can find plenty of information about PCB/system layout for high-speed USB. That's to be expected at 480Mb/s where things really are critical. However I haven't found much on USB full-speed layout (i.e. 12mb/s). What I'd like to do is have a standard USB 'B' receptacle in parallel with a proprietary multi-way connector. They will be mechanically arranged so that it will be impossible to plug both in. (If the user did manage to plug into both at the same time, all bets are off!) The standard USB 'B' must, of course, be certifiable as a USB full-speed device port, i.e. the effect of the stub running to the proprietary connector must be small enough so that USB compliance is not impacted. The proprietary connector will carry USB when the standard connector isn't used. As it is not "standard" it merely has to work, not to necessarily pass compliance testing, although the latter is obviously highly desirable. Oddly, I haven't found a reason why this won't work, provided I don't have the two connectors too far apart, and that I have separate series termination resistors for each connector. However, I'm still somewhat uneasy about this. Has anyone ever tried this an either made it work or found it not to work? I am aware that there are devices to support switching of the ports, but you know how BOM pressures are. But a higher BOM is better than a product that won't meet USB compliance. Thoughts? Andrew ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List technical documents are available at: http://www.si-list.net List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu