Let the maintenance partner come to the car, open the car key panel, remove the two signal lines of the original car speaker, and use a multimeter to perform voltage, short circuit and open circuit tests;

Voltage measurement: Use a multimeter voltage file to measure whether the two wires are charged. Normally, they should not be charged. If they are charged, check the accompanying cable line;

Short-circuit measurement: Notify the personnel in the equipment room to put the two signal lines of the telephone in the equipment room together. At this time, use the multimeter resistance to measure whether the two cables of the car conversation are connected. Normally, they should be fully connected. If no conduction, the accompanying cable is broken, or there is a conversion cable in the middle;

Open circuit measurement: ask the equipment room personnel to disconnect two signal lines, and measure with a multimeter resistance in the car. Normally, it should be completely disconnected (resistance value is infinite). If it is not completely disconnected, there is a short circuit in the signal line of the accompanying cable. All measurements are subject to 2 to 3 times. After the above test is correct, it can be directly connected to our car speaker LR.