Professor Hawking used an input device controlled by his cheek movements to choose the words he wanted to use. A special output device turned those words into electronic speech that people could hear.

Internal operating voltages in electronic devices continue to decrease, but input-source voltages don't change. As the difference between input and output voltages increases, so does the improvement ...

An isoquant shows combinations of capital and labor and the technological tradeoff between ... input, either labor or capital, can be substituted for the other while keeping the same output ...