My mom used a referee's whistle. There were 5 of us and the number of toots indicated which of the 5 she wanted (two toots for me). If we were outside playing in the neighborhood, we'd get alerted directly or indirectly from someone who was tired of hearing the whistle.

If it was dinner time and she needed us all, she'd blow 'Shave-and-a-haircut-two-bits'.