A decimal number to be carried on notifications of types 1 to 4 identifying the event which caused it. The format of this number is BBEEffCCT where BB is the number of the relevant MIB branch. EE indicates what type of event caused the notification. This value is dependent upon branch number and implementation. CC is the channel number which was the source of the notification. T discriminates the type of data, e.g. temperature. This value is dependent upon branch number and implementation. ff future use. Fields are packed with leading zeros and are set to zero if not relevant to a particular notification.