I searched the web and found some information about that switch.
Well, you live and you learn:
It really needs a driver when operating in 1pc-to-2printer mode!
The information I found is available here:
"The AF-142, when operating in 1 to 2 mode, uses the AS Ware driver to select which printer of the attached to the Auto Switch will print the print job. You can only be printing to one printer at a time unless both printers are identical and you wish to rapidly produce many copies of the same document."
The driver download page (available from the above site) is:
But hold it! This drivers is only for DOS/WIN of course... chances seem quite bad to get an OS/2 driver for it...