USB does not have a separate clock signal, Just data (two wire differential) and power. A PS/2 has both data and clock which are single ended signals. The mouse or keyboard must support both interfaces for those small adapters to work. If the device does not support both interfaces you can not just wire a differential signal into a single ended and expect it to work.

Here is a real converter. Check out the price...
http://www.blackbox.com/Store/Detail...KVUSB%C4%82PS2

We may be talking about different versions of the USB spec but in 1 and 2 one of the wires is +5V.

I charge my eReader, MP3 players and phone via USB.

Thanks for that adaptor link, this does what I thought my little green adaptors were doing.

Just out of curiosity, how can a keyboard support both PS2 and USB when it only has a USB cable and a little green adaptor with no electronics inside?

I don't know how it works except the mouse figures it out...

Hummm Very Interesting. I run a small PN (Personal Network) which consists of a Gateway/Firewall behind which 2-3 other computers are running -- usually a workstation, and "legacy" backup computer, and maybe a data storage computer. Having multiple keyboards and mice was a giant PITA. I bought a IOGEAR 4 port KVM (+A) controler. I use an old IBM 102 Model M Keyboard, and a Logitech TrackBall Mouse. I have Parkinson's Disease and Heavy and Stationary is important. The Logitech Mouse is a USB mouse, but comes with a USB --> PS/2 adapter. The Keyboard is a PS/2 keyboard plugs right in the PS/2 port of the KVM switch box; the PS/2 adapter plugs into the PS/2 Mouse port on the KVM switch box and the Logitech trackball mouse plugs into the adapter. The monitor hooks in, and so does the audio. Run the 4 pigtails to each of the computers. Each pigtail consists of a PS/2 Keyboard, PS/2 Mouse, Monitor, and Audio set of cables. to switch between computers simply hit [Ctrl] --> [Alt] --> [Shift] in that order -- FAST!!! Do it too SLOW and it does not record the entry sequence. If done correctly the Caps Lock and Scroll Lock lights will start to flash then enter the number of the computer (1-4) you wish to access and it will switch to that computer. This sure beats my former switch box which was via rotor dial. plus that did not have audio. The Logitech Trackball Mouse comes with its own adapter which is GREEN, so don't lose it.

What didn't you like about the rotor dial? The keyboard key sequence seems very counter-intuitive in comparison.

What about switch boxes that have 2 to 4 sticky buttons on them? Wouldn't like these either?

Actually the rotor dial was fine but it was manual which meant getting up, flip the switch to the desired computer, sit down, etc.. Standing up and sitting down has become harder as my Parkinson's has progressed, but actually the reason for switching was since it was a mechanical, something somewhere was no longer making a connection, and when it did connect it did some strange thing to the monitor image, until it got so bad I went in search of a new box. The IOGEAR was cheap enough so I went with my first , electronic KVM box -- now I don't even have to have to reach somewhere to punch a button, everything is done right from the keyboard: Entering Ctrl, Alt, Shift one at a time until the Caps Lock and Scroll Lock lights flash back and forth and entering the number of the computer (1-4) you want to access to is quite easy. The trick is entering the Ctrl, Alt, Shift sequence FAST so the the cap and scroll lights start flashing.

Without the cords etc the unit is about the size of a deck of playing cards which great. Probably the only thing I don't like about the unit is for some odd reason, they put the input connectors up front with the pigtail cables coming out the back. It would have been nicer if they had put two of the inputs -- say the PS/2 Keyboard and mouse on one side, and say the Monitor and Audio input on the other side, rather than front mounting all four. Still all in all this has proved to be an excellent little box.