The Block monitoring setting parameter prevents the relay from sending Class 1 events. Two blocking modes exist: the relay can keep or discard the occurring Class 1 events during the blocking period. In any case, every Class 1 data object updates its momentary value with the latest change event. A general interrogation following the blocking period always reveals the present state of all Class 1 data objects. When blocking mode is activated, it is reported by the IED with event code Fun 0 (=DevFunType) Inf 20. If the event buffer overflows during “Blocked Keep Events” mode, the oldest events are retained. The Block Monitoring parameter is found in .