Demons can smell like sulfur, roses, cologne...anything! They can also appear as: an angel of light, a dead person or child, a spirit guide, a healing spirit (reiki), an alien, a fairy, a dwarf, a spirit animal etc! We can't safely discern them! The safest thing to do, is let Jesus and his angels protect us.
The recommendation is therefore that the stimulation should be applied with a 2500Hz carrier medium frequency sinusoidal alternating current, burst at 50 Hz (10ms ON: 10ms OFF) at a maximum tolerable level.
A third possibility is to stimulate both nerve types at the same time by employing a burst mode stimulation. In this instance, the higher frequency stimulation output (typically at about 100Hz) is interrupted (or burst) at the rate of about 2 - 3 bursts per second.