Circuit switch S is closed after the integrated circuit TDA1024 trigger is turned on. Whenever the zero crossing of the mains
voltage generates a trigger pulse, bidirectional thyristor, full current flowing through the load Rl. When the switch S OFF no load current. To protect the Triac in parallel across its varistor. The maximum output power of the circuit is a 1400W, such as the use of thyristor BT139, output power up to 2000W, the use of BTW41, output power up to 5000W.