At present, three kinds of seismographs are used at Chinese seismic stations. They are the direct-coupled seismometer, the galvanometric seismograph, and the electronicseismograph.
目前，我国基准地震台上使用三种类型地震仪：直接耦合地震仪、电流计记录地震仪和电子放大地震仪。
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For overcoming the shortcoming of narrow output dynamic range of the electronic-amplifying seismograph, the Authors have designed a kind of circuit for automatic gain control.