elec. low power nightlight fusing/safety

Sounds like a fuse to me...

You mean the wiring within the unit is designed to melt like a fuse!!!! I don't think I can belive that one.

Fuses only really protect power leads, and as the device doesn't have a power lead (and it's going to fail open circuit long before the mains wiring gets warm) I don't think you need to worry :-)

Sometimes a weakness in a PCB link would act as a low current fuse...

I'm not worried - just interested - it seemed a little incongruous that's all.

Fuses come in a few different forms, some of which look nothing like traditional glass or ceramic fuses. But these types of products usually use a safety resistor instead. This is a series resistor that does 2 jobs.

1. it reduces inrush current
2. if it gets too hot it fails safely open circuit, thus acts like a slow thermal fuse.

These effectively give very low current fusing.

Thin PCB tracks will fuse too, but they would be limited to LV use, you wouldnt want to do that for mains fusing. A fuse wire link soldered into the pcb will have the same problem, burnt pcb would tend to bridge the fuse, so its not good enough on mains.

NT

Likely, the PCB itself would fail close to the pin connections if there was some form of overload.