What's so Special about these Humming Watches?
Accutron watches are unique in that they were the first electronic watches to dispense with the traditional "balance wheel and hairspring" as used in mechanical watches and other early battery powered watches. Hence they are of great historical interest, as well as still being a very practical and accurate means of timekeeping. Departing from tradition, they use a tuning fork, not unlike those used by musicians for tuning an instrument. They are inherently more accurate than balance wheel watches for a number of reasons.

The accuracy of a traditional balance wheel watch is dependant on many factors. Friction in the pivots (bearings) due to changes in the quality of the lubricating oil play a significant part in the ability of a mechanical watch to maintain accuracy and consistency of rate. Also, the condition of the mainspring and gear train driving it is very important. The rate of Tuning Fork watches is affected much less by lubrication, though it is still necesary for the correct functioning of the watch. The other major factors affecting accuracy of any mechanical watch are temperature changes and errors due to position (ie. how gravity effects it's operation in different orientations). Tuning fork watches are inherently far less affected by these problems. The fork has no bearings. It is far easier to "build in" temperature compensation into a Tuning Fork than into a circular balance wheel and it's hairspring. Gravity affects Bulova tuning forks in only 2 orientations (tines up and tines down) compared with the usual 5 positions of good quality balance wheel watches. (dial up, dial down, winder up, winder right, winder left). The tuning forks of the ESA movements have virtually zero positional error.

A balance wheel vibrates at usually 2 1/2 times a second, whereas the tuning fork hums at 300-720 times a second, depending on the model. Modern mechanical watches vibrate as fast as 5 times a second, in an attempt to improve their accuracy by making the balance wheel lower in mass and size, thus reducing their susceptibility to external influences.

Only Watchmakers of the highest skill can adjust a balance wheel watch for its best possible performance under all conditions. Repairing and adjusting tuning fork watches is considerably easier, as there are no adjustments apart from the index mechanism, which converts the vibrations of the tuning fork into rotary motion. Of course, skill and experience is still needed to adjust the index mechanism correctly.