If a system has two or more input variables and two or more output variables, simultaneous equations for the output variables can be written. In general, when the number of inputs and outputs is large, the simultaneous equations are written in matrix form.
Because most signals in the real world are analog but digital computers work on discretizations, it is necessary to convert between digital and analog signals. As mentioned above, this is done through digital-to-analog and analog-to-digital converters. Most approaches to digital-to-analog conversion use summers, where the voltages representing the digital bits are applied to input resistors, either directly or indirectly through switches gated on by the digital bits which change the input resistance fed by a dc source.Parent Post