There are many UR Multilin series universal relays with diverse functions and applications. The two Generation UR relays are the G60 and the G30. The G60 is designed for medium or large generators (primary and backup protection) and the G30 is designed for medium and small generators to provide comprehensive monitoring features in addition to protection of the generators. Additionally, the bulk of the UR relays fall into the transmission or distribution category. The L30 for example provides line current differential protection for sub-transmission lines whereas the D30 provides backup distance protection for transmission systems. There are more than eighteen UR relays in addition to the ones briefly mentioned here. Each of these universal relays is equipped with a CPU whether the universal relay is a vertical (3/4 size) or a horizontal mount relay. The CPUs can be identified by a RH-9 part introduction, followed by a letter that designates the specific characteristics of that CPU. The CPUs of the 9A, 9C, or 9D category will be of the old module types and the other letters (9E and up to 9S) will indicate a new CPU module contained in the universal relay.