Detection of a triac with a multimeter resistance R * 1Ω block, with red, black and two pen were measured between any two pins positive and negative resistance, the result of which two readings of infinity. If a group of tens of ohms, the group of red and black two-pin connection table for the first anode A1 and the gate G, the other foot is the empty second anode A2. Determine A1, G pole, and then carefully measured A1, G pole between positive and negative resistance readings that measure relatively small black table pen connects to pin the first anode A1, take the red pen pin the control electrode G. The black pen then identified a second anode A2, the red pen then the first anode A1 SCR, this time should not deflect the meter pointer, resistance is infinite. In the waveform controlled rectifier circuit, found within the forward voltage of the thyristor to withstand every half cycle, the first time issued a trigger pulse are the same, that is, the control angle α and conduction angle θ are equal, then the SCR T405-600T, single-junction transistor relaxation oscillator exactly how to cooperate with the AC power supply in order to achieve effective control? In order to achieve the rectifier circuit output voltage "controlled" SCR C106G, must bear a positive SCR to the voltage of each half cycle, the trigger circuit to send the first trigger pulse is the same all the time, this way of working with each other, called the trigger pulse synchronized with the power supply. How can we synchronize? We look at the regulator circuit diagram (Figure 1). Note that, here unijunction transistor relaxation oscillator power is taken from the output of the bridge rectifier circuit full-wave pulsed direct voltage. When thyristor does not turn, the relaxation oscillator capacitor C is charged power, UC exponentially rises to a peak point voltage UP when the unijunction transistor VT conduction, the conduction period of thyristor VS 2P4M, load RL the AC voltage and current, at the same time, VS turned down the voltage across the small, forcing the relaxation oscillator to stop working. SCR BTA225, are fertile Electronics (certified), SCR provided by the Dongguan City is Wal-Electronic Technology Co., Ltd. Dongguan City is Wal-Electronic Technology Co., Ltd. (www.dgmydz.com) (www.dgmydz.com) is Dongguan, FET leader, over the years, the company is implementing the scientific management, innovation and development, the principle of honesty and trustworthiness, the maximum limits to meet customer needs. Wal-electronics leader in the positive with the staff warmly welcome all inquiries negotiations to create a positive future Wal-electron better.