3 Pin Automotive Fuse
Darren Quinn 
I didn't know about these 3 pin fuses, we also take a look at LED 'smart fuses'
I've been delivering electrics training this week, and found some interesting info on fuses! Two things....
You can get fuses with an LED built in; when the fuse blows, it lights up! Called 'Smart Fuses'.
When everything is working ok, the fuse should have 12 volts on both sides, so the LED will not light up.
When a short circuit occurs, there will be 12 volts on one side, and ground on the other; the fuse LED will illuminate!
Someone mentioned they are useful for race cars where you need to be quick to identify a problem.
Apparently they have been around for a long time, I've never come across them before!
I also discovered 3 pin fuses!
The logic behind this invention is that it saves space inside the fuse box.
The 12 volt power supply is delivered on the centre pin, and there are 2 fuse filaments either side.
Everyday is a learning day!