The key diode is formed by fusing or silver filaments on a single crystal sheet of germanium or silicon. The characteristic is between the point contact diode and the alloy type diode. Compared with the point contact type, although the PN junction of the key diode has a slight increase in the capacity, the positive characteristics are particularly good. More switches are used, sometimes used in demodulation and power rectifier (not greater than 50mA). In the key diode, the fused Jin Si diode is sometimes called Jin Jian type, and the diode fused with the silver is sometimes called the silver bond.