Reader Feedback: What the L?

A Reader Reflects on Our Articles 'PLC Genesis', 'The History of the PLC' and 'History of Control; History of PLC and DCS'

By Carl Henning

Nice article from Jeremy Pollard ("PLC Genesis," June 2012). But my (possibly defective) memory recalls that originally Allen-Bradley called the device a PC for "programmable controller." Then IBM usurped the acronym, requiring the insertion of the "L."

Dick Morley's reminiscences initially refer to the Modicon 084 as a "programmable controller" ("The History of the PLC"). And I found one history that confirms my memory, but with Google I could probably find something to confirm anything ("History of Control; History of PLC and DCS").

Carl Henning,
deputy director,
PI North America, www.us.profibus.com

Pollard's fuzzy recollection: The very first piece of PLC literature I had my hands on was for a PMC (programmable matrix controller), which AB licensed from III (I think). The early 1970s is when the PLC arrived, and Odo Struger trademarked the acronym. I wouldn't disagree that the hardware was first referred to as a PC, but I believe it was changed for 'logical' reasons…no pun intended. The PC from IBM in 1981 was clearly after the PLC. That's my story, and I'm sticking to it!

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