A breath-powered callSourced
The old intercom began with a whistle
Speaking tubes carried voices through pipes. In versions with a removable whistle, blowing into one end summoned the listener at the other. The listener took out the whistle to answer. A breath could produce the call signal as well as the conversation.
The ringtone came from the caller’s lungs.
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Speaking tube · Wikimedia contributors
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Reviewed: 2026-10-05