 Welcome to Timing Diagrams. In this video, you'll learn how timing diagrams are used in digital electronics to show the operation of various circuits through graphs. In most situations, logic signals applied to the inputs of logic devices are not at stationary levels. Instead, they are voltages that change continuously between two states. To illustrate how logic gates respond to input signals in relation to time, timing diagrams have been developed. A timing diagram is a graphical method of showing the exact output behavior of a logic circuit for every possible set of input conditions. It is often used to describe the operation of digital devices because its visual characteristics are much easier to understand than a wordy explanation. The series circuit is used to show how a timing diagram operates. Two switches represent the inputs, and the light bulb represents the output. An open switch represents a logic zero, and a closed switch represents a logic one. The light bulb represents a logic zero when it is off, and a logic one when it is on. The format of the timing diagram above shows the condition during a given time period of each input switch and the output lamp on the vertical axis and the time on the horizontal axis. The diagram is read from left to right. Look at how the input and output waveforms correspond to the circuit operation for each highlighted time period. As you can see in the first time period, when both switches are open, the light is off. Notice that the bulb is only on during time period four when both switches are closed. Now, let's take a look at how the input and output waveforms for each time period correspond to the truth table and the signals at the logic gate. The series circuit with two switches operates the same way as a two input AND gate. Below is the AND gate, its truth table, and its timing diagram. More specifically, the timing diagram shows waveforms of the inputs A and B and the resulting output X over time. Look carefully. You'll see the same outputs for the AND gate and truth table. The diagram is sliced into five different time periods labeled T1, T2, T3, T4, and T5. In time period T1, inputs A and B are both high. Therefore, the output X is also high. Watch the highlighted time period and how it matches the AND gate and its truth table. Notice how the output X is high only when inputs A and B are both also high. Now that you've learned how timing diagrams operate for a two switch series circuit and its corresponding two input AND gate, select the answers that complete the statement correctly. First, read through the statement and then read through the potential answers. Pause or rewind the video if you need more time to think about your answers. Our first statement deals with how to interpret a timing diagram. The correct answers are output signal and input signals. This statement deals with where time is shown on a timing diagram. The correct answer is D horizontal. And finally, our last statement deals with the direction a timing diagram should read. The correct answer is A, left to right. Congratulations! You have completed the timing diagram video. Thank you for watching. If you liked this video, give us a thumbs up.