You may not think of salt and sugar as solids because when you see them in the kitchen they are such small particles. But each of these particles is as much a solid as a wooden table, a glass window, or a gold piece of jewelry. A solid is a collection of atoms or molecules that are held together so that, under constant conditions, they maintain a defined shape and size.
Pulse Width Modulation, or PWM, is a technique for getting analog results with digital means. Digital control is used to create a square wave, a signal switched between on and off.
Nielsen People Meter. People Meters are used in the top 25 markets (ranked by population). These homes are used for both national and local reporting (LPM = Local People Meters) and are an integral part of the 20,000 NPM homes. For markets 26-56, samples of 800-400 homes are recruited in each market.