The Blinking Light

Published in IEEE Spectrum Magazine, Nov 2008

I was considering buying a new desktop computer, and I thought I had found the ideal model with just the features that I wanted.  That is, until I noticed that one little thing was missing – the activity light for the hard drive.  The manufacturer probably saved a few cents by eliminating that one LED, but that little light was something of psychological importance to me.  How could I possibly buy a computer that was just going to sit there and not give me any indication that it was working?

A very long time ago, not long after the dinosaurs had gone extinct, I was working on modem design.  At the Bell System we had designed modems the way they were supposed to be – big, heavy clunkers with a telephone handset and embedded rotary dial.  They were just what the users of those days needed to connect to their time-shared mainframes.  But one day we were surprised when a competitor came out with a small modem that had an array of LED lamps on the front panel, indicating control signals like clear-to-send, as well as data activity.  “What user could possibly care about such things?” we joked among ourselves.

Well, it seemed that people did care about such things.  That little company sold a lot of modems, and pretty soon we had indicator lights on our modems too.  As a consequence, I learned a principle of design that I have never forgotten: people want blinking lights.

Too many electronic gadgets are inert steel boxes with stickers on the bottom that say something like “no user serviceable parts inside.”  Unless the box is interacting with the outside world in the way it’s supposed to, you have no idea whether or not it’s working.  When it doesn’t do what it’s supposed to do, you stare helplessly at the box.  “Are you alive in there?” you ask plaintively.  But such entreaties are a waste of breath; it isn’t listening or speaking.  You’d think that the box could at least hum or vibrate or something to communicate life.

A blinking light makes all the difference.  Even though you have no idea why it’s blinking the way it is, over time you become familiar with the light’s normal behavior.  It seems that over millennia humans have evolved a subconscious ability to recognize and categorize moving visual patterns, like the flash of tiger fur seen through dense foliage.  So it is with the activity light; there are familiar patterns and dangerous patterns.   I’ve had several cable modems go bad as well as several routers, and in every case I’ve recognized the problem in the unfamiliar blinking patterns of the activity lights.  “Ah ha,” I say to myself, “That box is sick.”

Quite often my computer is busy doing something that I have no clue about.  There is no visible activity on the computer screen, but I see the hard drive light blinking furiously.  What is it doing, I wonder?  At least the little light tells me that it is alive, though I worry about why it is so busy.  At such times I often wish that there was a special key on the keyboard labeled “what are you doing?”  I’ve always found the task manager rather useless for this purpose, and no human being could possibly interpret the gibberish that fills your screen following the dreaded “blue screen of death.”

Instead of an unintelligible binary dump, my imagined key would give a simple English description of what the computer was doing.  If you saw the hard drive activity light blinking frantically, you could ask for an explanation.  “I’m busy at the moment reformatting your hard drive,” it might say, “but I’ll be through in a jiffy.”  Or perhaps, “I’m just finishing the installation of the godzilla virus.” 

Once upon a time computers had lots of indicator lights, showing the activity on many of the backplane signals.  When you walked past a computer center, a dynamic light show was taking place inside.  “Wow, look at those things think!” you said to yourself.  Tapes spun and everything hummed.  Lights, action, camera!  But now it seems that the only indication of life is the roar of air conditioning.

So the computer that I had picked out to purchase had joined the growing legion of grey boxes devoid of charisma, the little activity lamp that was its only outward manifestation of personality having been sacrificed as no longer worth a few cents.  Maybe I’m the only one who cares about that light now, but I’m not buying that computer.  Their designers are probably joking among themselves, “What user could possibly care about such things?”  Well, for myself it’s déjà vu; been there, done that.

Robert Lucky