Understanding Frequencies for Power Conditioners
In power line conditioners and isolators, input and output frequencies are (typically) the same. Power sources are isolated from each other and typically from ground. The isolation can be general or very complete, depending on the application.
A government application of isolation is TEMPEST, which is a National Security Agency specification referring to spying on information systems through leaking emanations, including electrical signals.
While, in most applications, input and output phases (one or three phase) and voltages, e.g. 480 volts, remain the same, the same flexibility to change either or both remains, as in frequency converters.