- A small crystal of quartz accurately cut along certain axes so that it can be vibrated at a particular frequency, used for its piezoelectric properties to produce an electric signal of constant known frequency.石英晶体：沿某些轴线精确地切割成的一小块石英晶体，这样它能以一特定的频率振动，利用其压电的特性来产生稳定的已知频率的电信号