Different from BLDC (brushless dc motors), brush motors use only two connections instead of the three phases that BLDC motors use. In the case of a brush motor (shown here), only positive or negative DC voltage is applied. The voltage level, and polarity (positive or negative) dictate speed and direction. In figure 1 the ends of the armature are mainly repelled by both permanent magnet poles and attracted to the opposite magnet poles they are moving toward. In figure 2 the ends of the armature are equally repelled and attracted by both magnets. If the rotor does not have enough inertia to rotate beyond this point, then the motor is in danger of locking. For this reason 2 pole motors are not very popular and not often used. In figure 3, the ends of the armature are mainly attracted by both magnets and barely repelled by either magnet. The polarity of the magnets in the rotor will change when the split in the commutator ring passes beyond the brushes. At that point the current will be reversed changing the south pole of the rotor to north, and the north pole of the rotor to south.