The human brain works on electricity, but so do a lot of other things.
The mobile could be an electrical fault, could be the batteries on their last legs and giving out bursts of energy. When I was videoing fox cubs (they are now on Youtube if anyone wants a look) with a motion sensitive camera, which could be left out 24 hours a day, I would find all kinds of strange clicks and flashes and sudden transitions from full daylight colour to monochrome infra-red-lit night shots when the batteries were getting low. a new set cured it.
My landline phone was being peculiar, too. I tried everything, but remembered that I had had it for eight years and the rechargeable batteries were only guaranteed for 5. Replacing them solved that, too.
Also to be considered (don't want to worry you here, but if we are considering the supernatuiral, there are worries there too) is that thinking it detects odd smells is one thing that the brain does when its own electricity is playing up - for instance it is a forerunner of some epilectic fits.
Visual images are decoded in the brain, where an electrical discharge could be interpreted as whatever the viewer's mind decides, and Joan of Arc's voices may have been due to pressure on a specific part of the brain.