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One single packet of data if the Brits came by land, and two if they came by sea. It was a base 2 system. If you had the kind of high-school math that I had, you'll remember that base 2 mathematics does everything with only two possible states.
  technofile
Al Fasoldt's reviews and commentaries, continuously available online since 1983

Paul Revere did it first: The saga of digital signals


By Al Fasoldt
Copyright © 1991, The Syracuse Newspapers

   It's a little-known fact of history that Paul Revere was a big fan of digital video.
   Not that it was called video in those days, of course. And it wasn't even called digital. But I'm getting ahead of myself.
   Paul, as you know, was the early-warning radar, so to speak, for the renegade Colonials who were breaking away from the British at the start of the Revolutionary War.
   He could have used any regular method to warn his townsfolk that the Brits were on the way -- maybe even just yelling "The Brits are on the way!" would have worked fine -- but when the Redcoats arrived on the doorstep of history more than two centuries ago, Paul had a digital trick up his sleeve.
   It went like this, in the language of today's techno-speak:
   One single packet of data if the Brits came by land, and two if they came by sea.
   It was a base 2 system. If you had the kind of high-school math that I had, you'll remember that base 2 mathematics does everything with only two possible states -- off or on, up or down, 0 or 1. Something is either here or it is there; it is either a 1 or it is not a 1.
   Paul modified this in a clever way. First, he used light as his digital medium. Light travels a long way, and it is silent. It works a lot better than shouting in peoples' windows.
   Second, he knew intuitively that off-and-on digital methodology -- excuse me, I mean lighting the lamp or not lighting it -- could end up being very confusing. If the townsfolk had been told, "No lamp if they come by land, one lamp if they come by sea," his communications medium would have a flaw big enough to drive a tea chest through.
   What if the wind blew out the lamp? How would the rebels know the difference between an accidental zero state -- the lamp being snuffed out by the breeze -- and an intentional one -- a warning that the Redcoats were coming by land?
   So Paul settled on a base 2 system that started counting with 1. A single lamp meant one thing, and a double lamp meant something else. No lamp meant something was wrong with the signal.
   It was a neat way of getting around the problem of transmission errors. And, as we know now from the fact that we haven't had a king or a queen for quite some time, it worked perfectly.
   A modern textbook would describe the Revere method as having sufficient data integrity. Another kind of digital medium -- yelling from a rooftop, for example -- would have opened up the possibility of signal ghosting, in the form of echoes.
   Paul was smart in another way. He kept the medium separate from the message. That's something that makes digital techniques superior to analog ones. If he had used an analog method, he might have held up a couple of cardboard cutouts of Redcoats wearing combat boots if they were coming by land or carrying fishing poles if they were coming by sea.
   They would have had to be pretty big cardboard figures to see them all over town. And Paul might also have been faced with another analog problem -- if you are going to use an analogy to tell everyone that the enemy is on the way, shouldn't you make it as accurate as possible? Shouldn't you hold up a whole lot of cardboard figures if a whole lot of Redcoats were tramping toward town?
   Digital math made a lot more sense.
   It still does. The difference these days is that we tend to think of digital as something electronic, as in digital audio or digital video. And, of course, computers all work by digital math, too. All those bits that make up the bytes in your computer are either on or off, here or not here.
   But digital has been around a lot longer than your CD player or your PC. Obviously, Paul Revere might have a hard time figuring out how to play Paula Abdul on your Sony, and he wouldn't know how to get a WordPerfect program to indent an entire block of text, but he'd probably lend a sympathetic ear to the first digiphile who came along with praise for digital electronics.
   After all, he was lighting the way.