Odd USB Extension Cable
in [Mac Systems]
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From: Malcolm on 7 Jan 2010 23:21 On 2010-01-06 13:50:38 -0500, isw <isw(a)witzend.com> said: > Someone just "gifted" me with a large box of assorted cables. Among them > was an Apple-branded USB extension (male "A" on one end, female "A" on > the other) with the addition that the female connector has a little bump > sticking into the side of the socket so that no "ordinary" male USB plug > can be inserted. I'm told that this cable is for use with an Apple > keyboard (which presumably has a little notch to match the bump). > > Now, the result of this is that the keyboard's plug can be inserted into > *any* USB socket, while nothing *but* the keyboard can use the extension > cable. > > What's up with that? What is so special about that extension cable that > it must not be used for anything except that one keyboard? > > Isaac The notch also ensures that only one extension can be used with the keyboard. You can't daisy-chain them. This means Apple doesn't have to make the keyboard work with an arbitrary length of USB.
From: emelvy on 8 Jan 2010 00:03 On Jan 7, 11:21 pm, Malcolm <malcolm(a)invalid> wrote: > On 2010-01-06 13:50:38 -0500, isw <i...(a)witzend.com> said: > > > Someone just "gifted" me with a large box of assorted cables. Among them > > was an Apple-branded USB extension (male "A" on one end, female "A" on > > the other) with the addition that the female connector has a little bump > > sticking into the side of the socket so that no "ordinary" male USB plug > > can be inserted. I'm told that this cable is for use with an Apple > > keyboard (which presumably has a little notch to match the bump). > .. . . > The notch also ensures that only one extension can be used with the > keyboard. You can't daisy-chain them. This means Apple doesn't have > to make the keyboard work with an arbitrary length of USB. I have an Apple Keyboard M9034/LLA that I bought when another user (no names, please!) spilled orange juice on the one that originally came with my iMac G5 (iSight). The replacement keyboard came with a USB extension cable just as described above. Just as the OP was told, the cable connector that goes into the USB socket on the rear of the iMac has a linear depression on one side that mates with the bump on the connector of the extension cable; however, the socket on the iMac has no bump. The original keyboard supplied with the iMac did not come with an extension cable. I have never had a use for the extension cable because the cable molded onto the keyboard is 33 inches long, quite adequate for use with the iMac sitting on the table behind the keyboard. The length of the extension cable is about 39 inches (one meter, I suppose). If the computer had been of the kind one might place on the floor, then the extension might be necessary to use the keyboard on a table.
From: Matthew Russotto on 6 Feb 2010 17:59
In article <isw-AF94D7.10503806012010@[216.168.3.50]>, isw <isw(a)witzend.com> wrote: >Someone just "gifted" me with a large box of assorted cables. Among them >was an Apple-branded USB extension (male "A" on one end, female "A" on >the other) with the addition that the female connector has a little bump >sticking into the side of the socket so that no "ordinary" male USB plug >can be inserted. I'm told that this cable is for use with an Apple >keyboard (which presumably has a little notch to match the bump). > >Now, the result of this is that the keyboard's plug can be inserted into >*any* USB socket, while nothing *but* the keyboard can use the extension >cable. > >What's up with that? What is so special about that extension cable that >it must not be used for anything except that one keyboard? The USB spec doesn't (or didn't) allow extension cables. The cable actually works fine with other stuff if you force it or remove the bump. -- The problem with socialism is there's always someone with less ability and more need. |