The document discusses oscilloscopes, including:
1) An oscilloscope is a visual voltmeter that displays voltage patterns over time using a cathode ray tube (CRT) similar to a television screen.
2) There are several types of oscilloscopes including analog, digital storage, digital phosphor, and digital sampling oscilloscopes.
3) Oscilloscopes are used to measure signals and analyze waveforms, and can display different waveforms like sine waves. They have applications in measuring light intensity from a photocell and other signals.