My parents had a 'if you hear this whistle, come here', which, depending on the sequence of tones, meant anything from '5 minute heads up before it is time to go' to 'literally drop what you are doing and run to this position'.

It wasn't disrespectful at all. It was a great way to communicate over wider distances than is possible with regular voice, and in retrospect it was impressive how little translation it took for all of us kids to understand which meaning was being conveyed.