> entirely new concept. The new concept was power amplification: a small effort causing a larger than "natural" effect. E.g. you were always able to press a

> entirely new concept. The new concept was power amplification: a small effort causing a larger than "natural" effect. E.g. you were always able to press a button to tinkle a bell, but pressing a button and obtaining a sustained electrical ringing was new. Valves and transistors took it to the present stage, by cascading the effect of small inputs switching larger amounts of power from an external supply. (Yes, power amplification could be done mechanically before electricity with energy from water, weights, etc. but it was too cumbersome.)