From Wikipedia (
https://en.wikipedia.org/wiki/Fly-killing_device):
"Electric flyswatters (sometimes called mosquito bats, racket zappers,[14] or zap rackets) are hand-held devices that resemble badminton rackets or tennis rackets, which became popular worldwide in the late 1990s.[citation needed] US Patent 5,519,963 was awarded to Taiwanese inventor Tsao-i Shih in 1996 for such a device.[15] The handle contains a battery-powered high-voltage generator. The circuit is composed of an electronic oscillator, a step-up transformer and a voltage multiplier,[16] similar to the circuit in an electroshock weapon or stun gun, but with much lower power.
The grid of the flyswatter is electrically charged to a voltage of between
500 and 1500 volts (V) of direct current, activated by pressing and holding a button. When the electrically conductive body of a fly nearly bridges the gap between electrodes, a spark jumps through the fly. A capacitor attached to the electrodes discharges during the spark, and this initial discharge usually stuns or kills the fly. If the button is still pressed, the continuous current will roast and kill the fly. Many flyswatters have a three-layer grid to prevent people from touching both electrodes. The outermost grids or rods are at the same electrical potential, and are open enough to allow an insect to contact the inner charged grid.
Most electric flyswatters conform to electrical safety standards for humans:
a limit on the charge stored in the capacitor: a discharge of less than 45 microcoulombs (µC) is considered safe, even in the unlikely scenario that the current from a flyswatter would be flowing from one arm to the other arm, partly through the heart.[17] This means that the capacitor of a 1000 V flyswatter should be less than 45 nanofarads (nF). Due to this precaution for humans, the initial shock is usually inadequate to kill flies, but will stun them for long enough that they can be disposed of.
A limit on the current after the initial discharge: the maximal continuous current of most flyswatters is less than 5 milliamps (mA). This current is safe, even when flowing from one arm to the other arm of a human.[18]
An advantage over conventional flyswatters is that the electrical models do not have to mechanically crush the fly against a hard surface to kill it, avoiding the smeared mess this can create.[19] Also, the electrical grid can be relatively open, reducing air resistance and a rush of air that often deflects smaller insects around conventional swatters. Because of this, electric swatters can also be very effective in killing airborne mosquitos and "no-see-ums"."
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