Measurement Source used as active by an Analog Measurement. Possible values for this property are 1 -stScada: SCADA, 2 - stOperator: Operator (default), 3 - stCCLink: Control Center, 4 - stBilling: Billing, 5 - stCalculated: Calculated, 6 - stDatabase: Database, 100 - stTopologyProcessor: Topology Processor, 101 - stPowerFlow: Power Flow, 102 - stStateEstimator: State Estimator, 103 - stLoadShedding: Load Shedding, 104 - stDistLoadModelling: Distribution Load Modeling, 105 - stSelfHealing: Self-Healing, or 106 - stExternalReader: External Reader. The selected Source type must exist in the Measurement to be set as active. Users cannot select types 100, 101, 102, 103 , 104, 105, or 106 (Electrical Study outputs) if the StudyInputSource property is set to 0 (zero, Active Source). In case the selected Source is deleted, this property assumes a value of 2 (two, Operator).