A lamp dimmer circuit can be conceived in so many ways but the challenge is cost effectiveness and reliability. Thyristors (or SCRs) and TRIACs are the major components associated with the lamp dimmer circuit. Direct on line ( 120 VAC ) dimmers can be configured either by two TRIACs connected anti parallel or it can be configured by 4 number of SCRs in the same topology for a full wave phase control. But this is a costly methodology. The full wave phase control topology, as shown in the circuit was found in a RCA (Radio Corporation of America) power circuit book,1969. In fact, so far as power circuit is concerned, this is one of the cheapest effective typologies. A full wave rectifier bridge is being employed in series with the AC line along with a SCR, the rectified AC also had its zero crossing. The frequency of which is double that of the supply line and hence commutation of SCR at its natural zero is possible. Apparently it may appear that the SCR is working on a DC l...