DIRECT CURRENT (DC)
A type of electrical transmission where the charge flows directly from negative to positive poles, as in various kinds of batteries. Since there is no OSCILLATION involved in this current (it is often referred to as 0 Hz), it does not produce a HUM. However, direct current may fluctuate, for instance, as a time-dependent positive voltage, such as is used in a SOUND SYNTHESIZER as a control voltage.
Compare: ALTERNATING CURRENT. See: GENERATOR, PULSE, RECTIFICATION.
Sound Example: A DC elevator in an old building in Vancouver. Note the absence of electrical hum.