An analog audio signal is an exact copy of the sound itself. A digital audio signal, on the other hand, is the numerical form obtained by taking certain samples of the analog audio signal within a unit of time and converting these samples into a code consisting only of 1s and 0s. This allows it to be processed in systems such as computers. In digital audio systems, balanced cables are used. Impedance is important in digital systems. In these systems, cables have an impedance range of 110 ohms (±20%). For unbalanced (coaxial) cables, the impedance is 75 ohms. While low capacitance values are important in analog audio cables, in the transmission of digital audio signals, system impedance is the critical factor.