My name is Patrick Lecoanet I am the author of [Zinc]. Mail: lecoanet(at)cena.fr ---- An entirely different, but equally pertinent, meaning for PLC is "programmable logic controller" [http://en.wikipedia.org/wiki/Programmable_logic_controller]. As [KBK] has justly written, "PLC's and GPIO's [http://en.wikipedia.org/wiki/GPIO] - the bread and butter of a lot of Tcl'ers, including several Steves."