Defuse bomb?

I'm watching a movie on Netflix where tons of bombs are being defused. It's usually about removing the detonator.

Back in the movies, the thrill was always in the right cord. How can I imagine such a circuit that triggers the detonator when the "wrong" cable is cut.

Why are 5 wires sometimes used at all? Isn't two enough? Do you always have an electronic source of supply? Well ok, there are also mechanical switches that react to pressure.

I would just be interested.

No real USBV (Unconventional Explosive or Incendiary Device) looks like it does in the film

What does she look like then?

The idea is that the bomb maker wants to prevent the bomb from being defused. If there were only two cables, a battery and the detonator, that would be simple. Therefore - at least according to the respective story - such people build traps and hide how the ignition mechanism actually works.

One could imagine a (also quite simple example) that there are two circuits. When one is closed, the detonator is activated. The other circuit, however, must be closed so that a relay keeps the first circuit _open_. If a wire from the second circuit is cut, the first circuit closes and… BOOM!

Cool - thanks for the explanation