| 摘要 |
PROBLEM TO BE SOLVED: To obtain a communication method that enhances security, prevents a unit side reply device from being malfunctioned and uses a public channel. SOLUTION: An information collection unit 4 transmits a telephone call signal and disconnects it through a public channel 3 to unit side reply devices 2, each unit side reply device 2 stores a telephone call signal through the public channel 3, discriminates whether or not the stored call signal is an information request instruction from the information collection unit 4, and transmits a telephone call signal to the information collection unit 4 through the public channel 3 when discriminating it that the call signal is the information request instruction, and transmits information to the information collection unit 4 through the public channel 3 when confirming automatic incoming call from the information collection unit 4. According to this method, the unit side reply device 2 discriminates the information request instruction of the information collection unit 4, reconnects the public channel 3 and transmits information to the information collection unit 4. Thus, it is prevented that information is sent to a 3rd party from the unit side reply device 2.
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