The typical state of a switch is either connected or disconnected. Physically, there is no way for a switch to be connected more than once—it is either connected or it is not. In certain situations, however, it is useful to think of a connection as something that can happen more than once.
For example, consider having two tests that can operate simultaneously. Although these tests primarily use different instruments and test points, they share a connection from a power supply to the UUT power input. Instead of having to manually handle this shared connection by some extra component, it is preferable to create the two tests independently such that they could be operated individually or simultaneously. NI Switch Executive facilitates this sort of sharing with multiconnection.
You can make a connection with no multiconnection or multiconnect routes.
If a route is connected with no multiconnection, the route must be disconnected before it can be reconnected. If you try to connect a route that was connected without multiconnection, an error condition occurs.
If a route is connected with multiconnect routes, the route can be connected multiple times. The first connection call performs a physical hardware connection. Successive calls merely increase a reference count on the connection. Similarly, disconnect calls decrease the reference count. When the reference count is at 0, the hardware is physically disconnected.
When you add a route, you can set the default multiconnect mode for the route—Multiconnect Routes or No Multiconnect. If you do not set the default multiconnect mode, the mode defaults to Multiconnect Routes.
It is possible to share route legs as long as the routes share a common start or endpoint as shown in the following figure:
NI Switch Executive manages the legs internally, keeping the leg connected until it is no longer needed.