The “two flashing led” circuit is designed for 9 Volts but it works at lower voltages too. In this design we used red leds but by changing the series resistors R1 and R4 you can also use different LED ...

This is a simple blinking led circuit powered from 220V that can be used to mark special places or as voltage indicator. The voltage from the mains charges the capacitor through R1 resistor and D1 ...

Essentially, the circuit would be complete at this point, and three components would be sufficient for the function as a fuse monitor. However, with D3, another diode ensures that only half-waves ...