RE: ab switch problem.

Randy Smothers (
Mon, 29 Sep 1997 10:57:12 -0400

The potential for damaging something using a mechanical AB switch is
very real - one of my co-workers fried a HP LaserJet printer using a
cheap AB switch. In fact, HP's LaserJet manuals (and possibly DeskJet?)
state that the use of a mechanical AB switch with their printer voids
the printer's warranty. Other laser printer makers also recommend
against it.

The best option is to use an add-on card to add a parallel port to the
system. You can get one for only adding a second ECP/EPP/bidirectional
parallel port, using IRQ 5 or 7, for $20 or so (USA). A fancier one,
with a 83 byte buffer, and allowing use of IRQ's 5, 7, and 9 thru 15,
was $40.

If you don't have a spare slot, try an electronic AB switch, rather than
a mechanical one. These are $40 or more, but since they don't have any
moving mechanical contacts they can't short out your printer or camera.