| 摘要 |
PROBLEM TO BE SOLVED: To enable communication with each outer telephone equipment when a sub-unit performs communication with one of the plurality of outer telephone equipment. SOLUTION: A master unit 4 installed inside a residence 2 communicates with portable telephones 16a-16c outside the residence 2 and a porch sub-unit 6 installed inside or outside the residence 2. A panic button 12 disposed inside the residence 2 can perform radio communication with the master unit 4. When a call arises from the panic button 12, the master unit 4 enables communication between the portable telephone with which the porch sub-unit 6 communicates at present and the panic button 12 while the porch sub-unit 16 is in communication with one of the portable telephones 16a-16c. After the termination of the telephone call, another portable telephone is called. Then communication is enabled between the panic button 12 and the remaining portable telephones. COPYRIGHT: (C)2007,JPO&INPIT
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