This is what makes the UJT useful, especially in simple oscillator circuits. Working of Mock Flasher LED UJT 2N 2646 is used as a simple oscillator with the oscillating components R1 and C2. The LED ...

Figure 2 shows the current-voltage waveform of the circuit. Here are a couple of other examples. For a 5-V, ±5% monitor, set R1 = 121 Ω and R3 = 301 kΩ.

This is probably the simplest idea to generate flashing light from an LED using AC. The circuit is relatively the simple way of flashing one or more LEDs from a high voltage DC obtained from Mains.