A metal detector used to be an entirely analogue instrument, an oscillator whose frequency changed with the inductance of its sense coil when a piece of metal approached. [Łukasz Podkalicki ...

Unfortunately inductance is usually not a friend in these ... I briefly light up a nixie tube with a big ‘ole coil and a 9V battery. The demonstration is meant to show that inductors really ...

So, a copper coil that is used for either inductance, resistance or sometimes to move things, which is the electromagnetic properties of coils. So, it’s basically an old sub-supplier to IBM ...