Measurement Source used as active by a Discrete Measurement. Possible values for this property are 1 - wstScada: SCADA, 2 - wstOperator: Operator (default), 3 - wstCCLink: Control Center, 4 - wstBilling: Billing, 5 - wstCalculated: Calculated, 6 - wstDatabase: Database, or 100 - wstTopologyProcessor: Topology Processor. The selected Source type must exist in the Discrete Measurement to be set as active. Users cannot select the type 100 (output of a Hydraulic Study) 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).