Commonly referred to as the
fencepost error and occasionally called a "telegraph pole" or "lamp-post" error, it could just as well be called the
coil turns error. If you run an elevated feed-line 100m long with posts 10m apart, how many poles do you need? The intuitive answer 10 is wrong. The line has 10 elevated sections, but 11 poles as illustrated below.
This error often causes confusion when counting the number of turns on a coil. You start at the beginning of the coil, count turns along the edge to the other end, and total is 10. But the total number of turns is not 10; it is only nine, since you have to complete the first turn before you tick off number one, which ends at the second strand of winding that you encounter while counting, not the first. To avoid this error, count the first wire at the very beginning of the winding as the
zeroth turn.
But don't consider yourself
too stupid if you miscount turns or come up one short when ordering poles for the transmission line or posts for the fence, because of this simple error; you are in very good company. When the Romans first adopted the Julian calendar, adding the leap-year to more closely correct the progressive misalignment of the calendar with the seasons, the pontifices initially added a leap day every three years, instead of every four. According to Macrobius, the error was the result of counting inclusively, so that the four-year cycle was considered as including both the first and fourth years; perhaps the earliest recorded example of a fence post error. After 36 years, this resulted in three too many leap days. Augustus remedied this discrepancy by restoring the correct frequency of one leap day every four years. Of course, the Romans might be more easily forgiven for making this error than would a modern-day radio engineer; the Roman counting system has no zero. The lack of zero in Roman Numerals has been said to be one important reason that the Romans failed to develop industrial technology.
This also explains why we are in the 21st century, but the date on the calendar reads only two-thousand and something.
