12.1 Step functions can be used to define a window func- tion. Thus u(t + 2) - u(t - 3) defines a window 1 unit high and 5 units wide located on the time axis between -2 and 3. A function f(t) is defined as follows: f(t) = 0, = 5t, Ost = 10 s = -5t + 100, 10 s