The 4-pole NFZB auxiliary relays meet the latest standards for rolling stock and allow installation in passenger or driver's cabins of trains that frequently operate in tunnels or underpasses. They are used for switching auxiliary and control circuits. In doing so, they comply with all important standards for rolling stock: IEC 60947-4-1, IEC 60947-5-1, IEC 60077-1/-2, and applicable parts of the EN 50155 standards, as well as shock and vibration resistance according to IEC 61373 Category 1, Class B. They also achieve the highest levels in fire and smoke behavior while adhering to the European standard EN 45545-2 (HL2 hazard levels) in group assembly. The auxiliary relays allow direct control via ≥24V DC 500mA PLC outputs and require a very low holding power of only 1.7W. NFZB auxiliary relays can withstand short voltage dips and drops (according to SEMI F47-0706) between 24...250 V 50/60 Hz. They feature built-in surge protection and do not require additional extinguishing components.