Nonsinusoidal oscillators generate complex waveforms such as rectangular and sawtooth waves. Because the outputs of these oscillators are generally characterized by a sudden change, or relaxation, these oscillators are often called relaxation oscillators. The pulse repetition rate of these oscillators is usually governed by the charge and discharge timing of a capacitor in series with a resistor. However, some oscillators contain inductors that, along with circuit resistance, affect the output frequency. These RC and LC networks within oscillator circuits are used for frequency determination. Within this category of relaxation oscillators are multivibrators, blocking oscillators, and sawtooth generators.
Many electronic circuits are not in an "on" condition all of the time. In computers, for example, waveforms must be turned on and off for specific lengths of time. Square and rectangular waveforms are normally used to turn such circuits on and off because the sharp leading and trailing edges make them ideal for timing purposes.