Forward phase control (SCR)
The basic SCR dimmer will remain the choice for budget-conscious dimming installations for the foreseeable future. The simple technique of varying the switch-on point of the lamp current each half-cycle is established in tradition and is very cost effective.
The disadvantages of the technique include noisy filaments that can buzz audibly, and the possibility of cross-interference between dimmers and audio systems.
ETC's forward phase technology is the best in its class and boasts high quality choke designs on all its dimming products. Advanced options take dimming a stage further with high-risetime chokes to reduce the filament noise by slowing the rise time of the curve even more.