OT USB to PS/2 adapters

I have a relatively new (<1yr) PC without PS/2 keyboard & mouse
connectors. I've accumulated 4 USB to PS/2 adapters. Three are just 6"
cables with a USB male on one end and a PS/2 female on the other. The
fourth is similar, but has a large oval-ish thing in the middle of the
cable. My MS ergonomic keyboard has a PS/2 connector and will not work
when connected using one of the three plain adapters, but will with the
fourth.

I'd like to understand a) why, and b) where to buy a couple more of the
adapters that do work (for another project).

Any help from the incredibly knowledgeable PLUG-ers will be gratefully
appreciated.

Thanks in advance,
Mark Jarvis

---------------------------------------------------
PLUG-discuss mailing list - PLUG-discuss@lists.plug.phoenix.az.us
To subscribe, unsubscribe, or to change your mail settings:
http://lists.PLUG.phoenix.az.us/mailman/listinfo/plug-discuss