1. In general, a range of frequencies specified by the number of hertz contained within the band or by the upper and lower limiting frequencies. 2. The range of frequencies that a device is capable of generating, handling, or accommodating; usually the range in which the response is within 3 dB of the maximum response. For example, the bandwidth of a modulated signal or of a bandpass filter is commonly defined by the frequencies at which the power spectral density is 3 dB (or a factor of 2) less than that within the band. 3. The amount of frequency space occupied by a signal and required for effective transfer of information by the signal. In data transmission, the greater the bandwidth, the greater the capacity to transmit data bits.