According to the operation method, it can be divided into: rotary type, toggle type and lever type. Rotary switches are usually used. Each contact of the band switch is fixed on an insulating substrate. The insulating substrate is usually composed of three materials: high-frequency porcelain, which is mainly suitable for high-frequency and ultra-high-frequency circuits, because of its small high-frequency loss, but high price; epoxy glass cloth rubber sheet, suitable for high-frequency circuits and General circuit, its price is moderate, and it is widely used in ordinary radios and radio cassette recorders; paper rubber sheet, its high frequency performance and insulation performance are not as good as the above two, but the price is low. many. The purpose of the multiplex switch is that the input circuit is an oscillating circuit composed of an inductor and a capacitor. Discontinuously changing the inductance can change the natural frequency range of the oscillating circuit, that is, changing the receiving band.