The read-and-write head is employed to become aware of and adjust the magnetization of the material without delay under it. There is one head for every magnetic platter surface on the spindle, accumulated on a universal arm. An actuator arm or commonly known as access arm moves the heads on an curve transversely the platters as they rotate, allocating each head to get into almost the whole surface of the platter as it twirls. The arm is enthused with the use of a voice coil actuator or a stepper motor. Big drives read the data on the platter by feeling the rate of change of the fascination in the head; these heads had little coils, and succeeded in standard with a great deal like magnetic-tape playback heads.