Attempts have been made in the past to produce a sine wave output dimmer by using various semiconductor devices as the variable resistance, but each of these has run up against the difficulty of the available semiconductor technology not being able to handle the currents, voltages, and heat dissipation required for a robust, reliable production dimmer. The new wave of sine wave output dimmers has taken a different approach, using the switch-mode technology widely used in devices as diverse as the ballasts of many discharge luminaires and the power supplies of virtually all computers and lighting consoles. There are few companies which work on sinewave dimming field.Dynalite has been shipping the SVC (Sinewave Voltage Converter) dimmer since 1998. Bytecraft VST (Variable Sinewave Technology) won an award at PLASA 98. Jands Electronics has announced the development of a prototype of its SWDim sine wave dimmer. The principle behind all of these sine wave dimmers is very simple: The incoming mains is switched on and off between 600 and 1,000 times per mains cycle (30-50kHz) with the on time (width) of each pulse being proportional to the required output power from the load, a method known as Pulse Width Modulation (PWM). The very finely chopped output is then filtered back into a continuous waveform through an inductor similar to the choke on a phase control dimmer, but very much smaller, as the pulse frequency is higher. The shape of the filtered output waveform is almost identical to the input waveform, only its amplitude is different, precisely what happens in a resistance dimmer. Sinewave dimmer is very complicated electronic device. Only with a large number of sensors to gather data, a fast processor, and some clever software is it possible to maintain the complex dynamic equilibrium necessary for a sine wave dimmer to function.