If you’ve watch the Basil Rathbone Sherlock Holmes film Spider Woman posted earlier, you’ll’ve seen a speaking tube being used by the dodgy gypsy in the fun fair.
What a great invention that was invented in 10th century China (typo?)or maybe 19th century Italy or maybe Ancient Greece or maybe Ancient Rome. Who knows?
Below the video below is my all time favourite use of the speaking tube on film. Feeeeeb :o)