The simplest method is to use mechanical switch for conversion. You can buy a 4-terminal 3-gear switch, connect the core wire of the DAC copper shaft to the input end of the 3-gear switch, and connect the shielding wires together. Then, the core wires of the three signal sources are respectively connected to the three output terminals of the switch. When in use, just turn the switch to the corresponding terminal on the working equipment. Eliminate the trouble of plugging and unplugging wires. Make the thread as short as possible to avoid interference. At present, it is troublesome to use electronic conversion chip, and it is also assisted by chip power supply and control circuit.