| 摘要 |
PROBLEM TO BE SOLVED: To provide a security system that eliminates the need for updating the reception setting of a communication unit and can secure a backup line easily and inexpensively.SOLUTION: If a specific communication unit 3a coupled with specific detection means 2a cannot receive a communication signal d or the specific communication unit 3a coupled with the specific detection means 2a cannot communicate with a monitoring center 4 when the specific detection means 2a transmits the communication signal d, the other communication unit 3b other than the specific communication unit 3a processes the communication signal d transmitted by the specific detection means 3a and communicates with the monitoring center 4. |
