The User can cause any applied voltage to have a sinusoidal waveform or a line-section time dependence, such as a top-hat or saw-tooth waveform.
Or a User-supplied routine that gives the required time dependencies can incorporated. Examples are supplied with the CPO package.
The time-dependent fields are dealt with in the 'quasi-static' approximation. In other words, the program ignores any magnetic fields that are generated from the time variations of the electric fields (ie electromagnetic effects), and so the User must ensure that the frequency of the field is not too high and that the wavelength is much longer than the electrode lengths.