DC-balanced signals are used in communications systems to prevent bit errors when passing through circuits with capacitive coupling or transformers.
Bit errors can occur when a series of 1's create a DC level that charges the coupling capacitor, bringing the signal input down incorrectly to a 0-level.
In order to avoid these kinds of bit errors, most line codes are designed to produce DC-balanced signals.
It occurs in the capturing of sound, before it reaches the recorder, and is normally caused by defective or low-quality equipment.
Either the loudest parts of the signal will be clipped prematurely since the base of the waveform has been moved up, or inaudible low-frequency distortion will occur.
[3] On a voltage-controlled oscillator (VCO), such as in a radio transmitter, selection of the center frequency of the carrier wave is done with a DC bias.