I know both can graph waveforms but I'm a bit confused about what spectrum analyzer graphs tell you. I read an explanation that says http://www.andrew.cmu.edu/user/ebuehl/robosapien-lirc/oscilloscope.jpg [Broken] That I understand but the explanation of spectrum analyzers is a bit more complicated For the oscilloscope the graph shows 1 frequency, 1 cycle, 1 period. It shows the exact magnitude of the wave at every point in time throughout the cycle so obviously its magnitude over time. When they say magnitude over frequency what exactly do they mean? If you were only measuring 1 frequency like you were with the oscilloscope would only 1 line appear? Are spectrum analyzers only used for observing the magnitude of multiple frequencies at once?