Use batteries to judge ordinary thyristors

Take four 1.5V batteries and connect them in series, tap at 1.5V and connect switch S. The positive electrode of E1 is connected to the anode of the ordinary thyristor VS through the lamp HL. The negative electrode of E2 is connected to the cathode of VT. When S is closed, HL will not go out. Because the resistance of the bulb is small, the current flowing through VT is sufficient to maintain the current that continues to conduct after it is triggered. Only after disconnecting the anode or cathode connection of the ordinary thyristor, VT will be turned off and HL will be extinguished.