Fig.B.3 gives the signal flow graph for the general onepole filter. The road to the frequency response goes as follows:

The onepole filter has a transfer function (hence frequency response) which is the reciprocal of that of a onezero. The analysis is thus quite analogous. The frequency response in polar form is given by
A plot of the frequency response in polar form for and various values of is given in Fig.B.4.
The filter has a pole at , in the plane (and a zero at = 0). Notice that the onepole exhibits either a lowpass or a highpass frequency response, like the onezero. The lowpass character occurs when the pole is near the point (dc), which happens when approaches . Conversely, the highpass nature occurs when is positive.
The onepole filter section can achieve much more drastic differences between the gain at high frequencies and the gain at low frequencies than can the onezero filter. This difference is achieved in the onepole by gain boost in the passband rather than attenuation in the stopband; thus it is usually desirable when using a onepole filter to set to a small value, such as , so that the peak gain is 1 or so. When the peak gain is 1, the filter is unlikely to overflow.^{B.1}
Finally, note that the onepole filter is stable if and only if .