Air conditioning system

An air conditioning system, comprising:

• a plurality of air conditioners;
• and
• a communication line interconnecting the plurality of air conditioners, wherein
• the communication line is a core wire included in a cable including a shield,
• each of the plurality of air conditioners includes
• a direct current power supply to generate a power supply voltage being a direct current voltage,
• a communication circuit drivable by the power supply voltage generated by the direct current power supply,
• a terminal block to connect the communication line to the communication circuit, and
• a metal housing accommodating the terminal block and a portion of the cable in which the core wire is not covered with the shield,
• the communication circuit communicates with another communication circuit with a communication method using a radio frequency signal through the communication line,
• the shield is connected to a ground of the communication circuit at each of two ends of the cable, and
• the metal housing has no opening longer than a length threshold corresponding to a wavelength of the radio frequency signal.