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olrob · 03-04-2008, 12:42 PM

Win XP home SP2.

I have overcome (not solved) the problem. I talked to a tech for a firm that sells adapters and hubs. He assured me that the adapter only has straight through connections from pin to pin. He also said usb connections can be fickle. Two cables with an adapter between should work between a device and a pc as long as the total length is no more than about 5 meters. But the adapter can present an interference/impedance/mismatch (connector to connector twice) and if not shielded can pick up some signal interference.
My initial try was 2 cables (A & B) and adapter between an external hard disk (EHDD) and a pc's usb port which only worked when I used a hub. Next, I tried 2 different cables (C & D) and adapter between my printer and pc and, to my surprise, it worked. I surmised that both cables and adapter were matched somehow. I then took one of these cables (C) and replaced the original adapter to pc cable (A) and (again to my surprise) it worked. Cable A was compatible with the hub (which also reconstructs the signal as explained by MOJO) but not the adapter.
When I used cable A, adapter and cable D with my printer to pc link it also worked.
I now have a link to the EHDD and another link to the printer and I can switch them (manually disconnect one cable and connect another) to either pc. I also demonstrated that "hot-switching" peripherals can work fine.

Thanks for all your help. I hope this explanation can also help any newbe that has usb cable problems.

03-04-2008, 12:42 PM	#10
olrob Member (4 bit) Join Date: Mar 2008 Location: Near Boston Posts: 10	Win XP home SP2. I have overcome (not solved) the problem. I talked to a tech for a firm that sells adapters and hubs. He assured me that the adapter only has straight through connections from pin to pin. He also said usb connections can be fickle. Two cables with an adapter between should work between a device and a pc as long as the total length is no more than about 5 meters. But the adapter can present an interference/impedance/mismatch (connector to connector twice) and if not shielded can pick up some signal interference. My initial try was 2 cables (A & B) and adapter between an external hard disk (EHDD) and a pc's usb port which only worked when I used a hub. Next, I tried 2 different cables (C & D) and adapter between my printer and pc and, to my surprise, it worked. I surmised that both cables and adapter were matched somehow. I then took one of these cables (C) and replaced the original adapter to pc cable (A) and (again to my surprise) it worked. Cable A was compatible with the hub (which also reconstructs the signal as explained by MOJO) but not the adapter. When I used cable A, adapter and cable D with my printer to pc link it also worked. I now have a link to the EHDD and another link to the printer and I can switch them (manually disconnect one cable and connect another) to either pc. I also demonstrated that "hot-switching" peripherals can work fine. Thanks for all your help. I hope this explanation can also help any newbe that has usb cable problems.