Communication in which a digital signal is placed directly on the transmission medium without requiring a carrier, i.e. without modulation. Only one signal may be present on the baseband channel at a time. This type of signalling, baseband signalling, is also called d.c. signalling because in some baseband networks a continuous d.c. voltage is present when the data does not change. Baseband networks may use twisted pair, coaxial cable, or optical fibre for data transmission. Compare broadband networking.