Tom’s laptop is sold as a computer, not as a radio station, and so it might seem odd that it should be radiating anything at all. It is all a byproduct of the fact that computers are binary critters, which means that all chip-to-chip, subsystem-to-subsystem communication taking place inside the machine—everything moving down those flat ribbons of wire, and the little metallic traces on the circuit boards—consists of transitions from zero to one and back again. The way that you represent bits in a computer is by switching the wire’s voltage back and forth between zero and five volts. In computer textbooks these transitions are always graphed as if they were perfect square waves, meaning that you have this perfectly flat line at V 0, representing a binary zero, and then it makes a perfect right-angle turn and jumps vertically to V=5 and then executes another perfect right-angle turn and remains at five volts until it’s time to go back to zero again, and so on.