Fire Brigade lookout with speaking tube, 1887.
© Science Museum / Science & Society Picture Library
Plate from the Illustrated London News. Charles Babbage (1791-1871) evisaged a system whereby communication via tubes would take 17 minutes to travel from London to Liverpool. The human voice was used to open or close a valve which regulated the electric current. The microphone, a carbon ball resting on three carbon points at the end of a speaking tube, resembled a mechanical ball valve. Telecommunications were becoming more widely used following the redesigning of the telephone by the American scientist and inventor Thomas Alva Edison (1847-1931) shortly after its invention by Alexander Graham Bell (1847-1922) in 1876.