The BJT H bridge allows a mixed counter polarity led chain to be lit on by fast switching. This is the case of many Christmas chain lamp decorations easily purchasable in any commercial center.
Nevertheless supplied controllers emit a wide range of disturbing frequencies you may not want affecting your radio equipment antenna.
Moreover those effects are provided by a little microprocessor that does not let you know how the device works.
Here is an alternative to that way:
The pilot signal duty cycle establishes the illumination of each polarity led chain while the frequency sets the brightness of the whole led chain. The load polarity is reverted
and back too the previous condition quickly, so our eyes cannot see the light discontinuity. On purpose circuitry, made by a NE555 configurable circuitry is often seen as a good solution.
