| 摘要 |
PROBLEM TO BE SOLVED: To enable the called side to immediately confirm the failure of radio connection at call holding and transfer to an extension cordless telephone set. SOLUTION: If a failure of radio line connection of an extension cordless telephone set for the transfer destination is detected by a radio line state monitor part 5, a key telephone system 1 sends alarm tone sounding information to an extension cordless telephone master set 14. When receiving the alarm tone sounding information, the master set 14 starts sounding of an alarm tone from a speaker 27 to report the failure of radio line connection.
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