A new-to-me "Don't use those horrible words"

James A. Landau JJJRLandau at AOL.COM
Wed Nov 26 15:58:31 UTC 2003

In a message dated >  Tue, 25 Nov 2003 13:11:07 -0600,  Dan Goodman <
> dsgood at VISI.COM> complains

>  The County of Los Angeles has requested that equipment vendors
> avoid using the industry term "Master/Slave" in product descriptions and
> labelling.

This particular taboo popped up long before political correctness became,
well, politically correct.

The widely used LORAN navigation system (which dates back to just after World
War II and is still in use) works as follows:  station A broadcasts a pulse.
When station B hears this pulse, it broadcasts a similar pulse.  Same for
stations C and D.   Using the arrival times of these pulses, your LORAN set can
figure out exactly where you are.

(Mathematically:  the locus of all points whose difference in distance from
two fixed points (called the "foci") is constant is a hyperbola.  Hence the
difference in arrival time for the pulses from A and B locates you on a
hyperbola, and which pulse arrives first tells you which branch of the hyperbola you
are on.  The difference in arrival times for A and C locates you on a branch of
a different hyperbola.  The two branches can intersect in only two points.
Dead reckoning, or the A-D hyperbola, will tell you which of those two points
you are at.)

Originally station A was called the "master" and stations B, C, and D were
the "slaves".  Currently there are LORAN chains covering most seacoasts between
the Arctic and the Tropics.  Since the stations are a few hundred miles apart,
it is common for them to be in different countries.  The terminology had to
be changed so that A was the "primary" and B, C, D were "secondaries", because
"no one wants to be a slave to a foreign master!"

I don't know when the terminology change occurred.  I discovered it during a
research project in 1985---if you're really interested, I can dig out my

            James A. Landau
            systems engineer
            FAA Technical Center (ACB-510/BCI)
            Atlantic City Int'l Airport   NJ   08405   USA

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