I've been researching some topics in the history of electronics, and as I was digging around, it crossed my mind that the word "analog" has an interesting history itself. Its definition and use changed several times during the twentieth century. In the 1989 print edition of the Oxford English Dictionary, the only engineering use of the word analog (of course, they spelt it "analogue") was as an adjective before the word "computer":
ANALOGUE --- (adjective) analogue computer, a computer which operates with numbers represented by some physically measurable quantity, such as weight, length, voltage, etc.The 2013 on-line edition has a much improved and expanded entry for the word, which includes
ANALOGUE --- (adjective) typically contrasted with digital... 1c. of signals or data: represented by a continuously variable physical quantity, such as voltage, spatial position, etc.However, in the context of circuit design and signal processing, I prefer the definition
ANALOG --- (adjective) in signals, continuous in amplitude and time; in circuit design, circuits that operate on these signals using continuous quantitiesas opposed to
DIGITAL --- (adjective) in signals, quantized in amplitude and discrete in time; in circuit design, circuits that operate on discrete-time signals using quantized (usually binary) representations.I don't insist these definitions are exhaustive or complete(1), but they draw a line in the sand for the starting point in this archaeological dig.
So, when did the meaning of "analog" change from "scale model" to its modern definition? I plan to find out. One interesting way to trace the evolution of the word is to find when it became commonly accepted enough to appear in the titles of publications, rather than in the text, where its meaning could be easily defined with a footnote or parenthetical phrase(2).
I've been digging around a little bit, and I've found some interesting things, and about which I have many comments, which I will share over the next few posts.
Can't wait? Here are some early findings: The first published articles to use the word "analog" (as a noun) in the title were a pair of papers by H. H. Skilling of Stanford University in 1931:
 H. H. Skilling, "An electric analog of friction for solution of mechanical systems such as the torsional-vibration damper," Transactions of the American Institute of Electrical Engineers, vol. 50, no. 3, pp. 1155-1158, Sep. 1931.The first published article to use the word "analog" as an adjective in the title was published in 1948:
 H. H. Skilling, "Electric analogs for diffi cult problems," Electrical Engineering, vol. 50, no. 11, pp. 862-865, Nov. 1931.
 E. L. Harder and G. D. McCann, "A large-scale general-purpose electric analog computer," Transactions of the American Institute of Electrical Engineers, vol. 67, no. 1, pp. 664-673, Jan. 1948.The first book(3) to use the word "analog" in the title was the classic text by Korn and Korn in 1952:
 Granino A. Korn and Theresa M. Korn, Electronic Analog Computers. New York: McGraw-Hill, 1952.Analog Devices, Inc. was founded in 1965, see:
 Walt Jung, "Op amp history," in Op Amp Applications, Walter G. Jung, Ed. Norwood, Mass.: Analog Devices, 2002, ch. H, p. H.35.The first books to use the words "analog" and "circuit" in the title were published in 1972:
 Dan Sheingold, "Editor's notes: Analog dialectic," Analog Dialogue, vol. 30, no. 3, p. 1, 1996.
 Alan B. Grebene, Analog Integrated Circuit Design. New York: Van Nostrand Reinhold, 1972.If you have additional (or contradictory!) information, please leave a comment.
 Jacob Millman and Christos C. Halkias, Integrated Electronics: Analog and Digital Circuits and Systems. New York: McGraw-Hill, 1972.
- For example, switched-capacitor filters are continuous in amplitude and discrete in time, and asynchronous digital systems do exist.
- This approach has the added bonus of being easier to research, given modern searchable databases, so it makes a good starting point (but just a starting point).
- I define "book" to mean published by a major publishing house for public distribution. Technical reports, computer manuals, and theses don't count.