Type IAC relays are used in the protection of industrial and utility power systems against either phase or ground overcurrent. They are single phase (although some models contain more than one unit), non-directional, current sensitive, AC devices. The basic operating mechanism (the time unit) produces one of several available operating characteristics. The operating time is inversely related to operating current which permits close coordination with other protective devices. It consists of a magnetic core operating coil, an induction disc, damping magnet, and a mechanical target. The IAC relay may also include one or more hinged armature instantaneous overcurrent units, with integral target.