Resonator Resonator A resonator is a device or system that exhibits resonance or resonant behavior, that is, it naturally oscillates at some frequencies, called its resonant frequencies, with greater amplitude than at others. The oscillations in a resonator can be either electromagnetic or mechanical (including acoustic). Resonators are used to either generate waves of specific frequencies or to select specific frequencies from a signal. Musical instruments use acoustic resonators that produce sound waves of specific tones. Another example is quartz crystals used in electronic devices such as radio transmitters and quartz watches to produce oscillations of very precise frequency. A cavity
Cassandra (metaphor) representing the human moral conscience whose main task is to issue warnings. Cassandra as moral conscience, "predicts ill to come and warns that punishment will follow and grief arise". Cassandra's need to point out moral infringements and subsequent social consequences is driven by what Klein calls "the destructive influences of the cruel super-ego", which is represented in the Greek myth by the god Apollo, Cassandra's overlord and persecutor. Klein's use of the metaphor centers on the moral nature of certain predictions, which tends to evoke in others "a refusal to believe what at the same time they know to be