The OPC client capability that is built into the Instrumentation ActiveX controls is intended to reduce your engineering time by taking advantage of the capability provided by OPC to browse the available items in an OPC server and select an item for the OPC server to then notify the client application of any changes to the chosen item. When you place a copy of one of the objects in the Instrumentation ActiveX library into your container, one of the options on the custom properties pages is an OPC tab. From this intuitive interface you can connect to local or remote OPC Data Access servers and browse for available items. (more details) Once you have completed this point and click configuration and run your application, the Instrumentation ActiveX controls will connect to the specific OPC Server(s) and subscribe to the chosen items at the specified update rate.  The OPC Server(s) will make a call back to the Instrumentation Objects automatically (no user code needed) whenever values change.  If the value of a property in the Instrumentation ActiveX control that is connected to an OPC item changes, the control will automatically write that value to the OPC server using an OPC Synchronous write. Multiple properties on an object can be bound to multiple points on a single OPC server or multiple points on different OPC servers, both local and remote. NOTE: For Remote OPC Server connections you should configure DCOM according to our DCOM Tutorial. For users wanting programmatic control over the OPC connections, we have exposed a set of properties that allow you to add OPC connections dynamically at runtime and activate/deactivate them programmatically.