Having alternating currents of two different frequencies that are combined to produce two new frequencies, the sum and difference of the original frequencies, either of which may be used in radio or television receivers by proper tuning or filtering.

• 外差的由两股不同频率的交替电流联合产生两个新的频率的，原频率的总和及差拍均可通过适当调频或滤波用于无线电或电视接收