such shunt devices cause u2018 flickering u2019 in series wired light strings of the remaining bulbs when only ten or fifteen percent of the bulbs are of the flashing or twinkling type while it may appear that the sharper the turn on the better the voltage regulation and the better for random twinkling that is not the case in actual practice with reasonable device tolerances it is not desirable to use sharp turn on devices in series wired light strings with flasher bulbs installed for random twinkling because a sharp turn on device creates undesired flickering when too many twinkle lights are added which affects the remaining non flashing lights consequently rounded knee devices are preferred in such a string of lights even though more current may be consumed most of the series wired mini lights today operate with 140 to 200 milliampere bulbs at between 2 5 and 3 5 volts standard off the shelf zener diodes have too small of a silicon chip area to give the required rounded knee iv characteristic that these bulbs need for desired random twinkling the use of larger area chips comes at a performance price while the lighting effects are much better the current dissipation is increased and more power is used to achieve these benefits leakage currents of.