Earth fault monitors are used for earth fault monitoring in unearthed AS-i and 24 V DC systems. A volt-free relay output signals the existence of an earth fault. This prevents dangerous situations such as inadvertent machine starts. An insulation fault monitor detects both symmetrical and asymmetrical earth or insulation faults. A flashing yellow LED signals symmetrical, a permanently lit LED asymmetrical faults. The evaluation "earth fault / insulation fault present" can be executed via two volt-free signal contacts.