Frequency converter. Com refers to the serial communication port on the car. The connection mode is that the remote controller controls the contactor, and the contactor controls the frequency converter. The frequency converter is controlled by four control lines: COM (male * * * line), x 1 (forward rotation), x2 (reverse rotation) and x3 (multi-speed), and x 1 turns off the driving motor to rotate forward. The remote control receiving part of the alarm system is used to receive the control signal sent by the remote controller, and its function is to complete the frequency selection, amplification, demodulation and shaping of the high-frequency signal, and output the control pulse sequence.