Bool indicator is "True" if I connect this indicator to terminal. (In case structure)

[crossrulz]

You have to tell the tunnel what to output in the FALSE case as well.

[altenbach]

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@Lugaro wrote:

My original problem is VI for bar-code scaner.

I scan bar-code and wont to see it while I dont use scanner. But string indicator clear in next cycle. Somtime (and today) it work as I wont. Sometime case work evry cycle after start - clear "string" and ON "test" indicator   

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You really need to start with the tutorials and look at the shipping examples. There are also great talks about serial communications.

• There is an "empty string?" primitive. (There is also a >0 primitive)
• Why do you use "bytes at port"? Isn't there a termination character?
• Why don't you attach your VI? We cannot see what's in the FALSE case, for example.
• Do you really need to configure, read and close the serial session with every iteration of the loop? (I assume there is a toplevel loop, or are you using "continuous run mode? Don't!!!)
• Why is there even a case structure?