The effective carrying capacity of a telecommunications transmission medium. Bandwidth describes how much information can be pushed through an electronic "pipe" at any given time. In analog systems, it is the difference between the highest frequency that a channel can carry and the lowest, measured in hertz. In digital systems the unit of measure of bandwidth is bits per second. For instance, a voice transmission by telephone requires a bandwidth of about 3000 cycles per second (3KHz). A TV channel occupies a bandwidth of 6 million cycles per second (6 MHz) in terrestrial Systems. In videoconference based systems a larger bandwidth of 17.5 to 72 MHz is used to spread or "dither" the television signal in order to prevent interference.