I had misread the order of the letters and instead of ELO, it really read "EOL System". Of course, that acronym meant something else entirely, which is battery End-of-Life indicator. It was designed to let the user of a quartz watch know that the battery is low. See the video here.
Swiss Army devised a clever visual trick as a warning sign. As we all know, the normal operation of a quartz watch shows a ticking seconds hand that jumps from one position to the next on the watch dial. Sixty ticks equals sixty seconds, which equals on minute... and so forth.
For the End-of-Life system, the seconds hand takes giant leaps every 4 seconds. It takes 15 leaps of this hand to complete a full minute. The wearer simply cannot miss this because it looks so peculiar. I said visual trick, because the watch will still keep accurate time. I would be curious if skipping 3 hand positions for every 4 seconds extends the life of the already low battery. That's a good question, but I have no information on that.
This system takes the guess work out of planning a battery change. This is helpful for watches that have batteries that can last many years. Heck, I have watches with batteries older than some of my friends' children. If only other things gave this kind of warning like toilet tissue or staplers!