Baseband systems are systems that operate without carrier frequencies, i.e. with unmodulated signals, with signals in their original frequency position.
In baseband systems, the frequency spectrum of the transmitted signal and the bandwidth it occupies are directly dependent on the transmission speed, but can vary greatly depending on the transmission method used. Thus, in baseband technology, there is no fixed or limited frequency band. For example, the baseband for audio signals is between 50 Hz and 18 kHz, and for video signals between 0 Hz and 5 MHz.
Digital signals are fed directly into the cable or optical fiber in the form of pulses and occupy all or part of the cable's bandwidth, leaving the other part unusable for other services. In order to transmit signals in the baseband, there are several transmission and modulation methods. For example, intensity modulation with laser diodes or light-emitting diodes.
Baseband systems thus offer only one channel, which must be logically tailored to the various needs. Opposite: broadband.