TABLE OF CONTENTS If a slowly increasing voltage is put on the horizontal terminals and plates, the visible spot will move slowly across the screen. When the spot gets to the right-hand side, the voltage is arranged to then quickly decrease to zero, so the spot "flies back" to the left-hand starting position. This voltage versus time "signal" that goes to the horizontal plates comes from an internal "signal generator" which is part of the whole oscilloscope system, and its "waveform" is shown in the diagram of Fig. 8.2.
The person using an oscilloscope can control the speed with which the "horiz." voltage builds up, and if it is very slow, the spot of light will only creep across the screen toward the right, then flying back to the left and then creeping across again, over and over. If it builds up and then repeats very fast, a bright line will appear on the screen, since the human eye will merge any motions into a single image, if they repeat faster than about 50 times per second.
Now suppose that another, completely external sawtooth signal generator is being tested, possibly a new one that was built by the experimenter. (In fact, this will be done in a later chapter. Devices that generate unusual waveforms are sometimes called "signal generators" or "function generators.") If that external sawtooth signal is fed into the vertical
