Both lamps are neon bulbs ( 100V@0.5mA = 50mW ) the series resistors are selected for 240V ( 340V peak ) mains supply. The top lamp lights when the fuse blows ( switch opens ) the other lamp lights when power is reaching the load as normal ( switch closed ) 10K is the minimum load and if load is lighter the 10K would need to be added.
Can be adapted for low voltage circuits using LEDs ( low current ) instead of neon bulbs.
