Continuous-Time and Discrete-Time Signals A signal is said to be a continuous-time signal if it is defined for all time. Continuous-time signals are defined for a continuum of values of the independent variable. A discrete-time signal is defined only at discrete instants of time.Thus,the independent variable has discrete values only,which are usually uniformly spaced.Continuous-Time and Discrete-Time Signals • A signal is said to be a continuous-time signal if it is defined for all time. • Continuous-time signals are defined for a continuum of values of the independent variable. • A discrete-time signal is defined only at discrete instants of time. Thus, the independent variable has discrete values only, which are usually uniformly spaced