| 摘要 |
PROBLEM TO BE SOLVED: To provide a telephone set that can efficiently select a line. SOLUTION: A system phone 1 is connected to the same line to which other system phone 1 available of communication with the phone 1 and a telephone set 2 not available of communication. The system phone 1 comprises a line voltage detector 12, a line state discriminator 13, a timer 14, a transmission reception control section 15, a phone kind discriminator 16, and a terminal control section 17. The line voltage detector 12 detects a voltage of the line and a line state discriminator 13 discriminates whether or not the line is in use on the basis of the voltage. The timer 14 starts counting a prescribed time in timing at which the use of the line is started. The terminal control section 17 discriminates whether or not state data received by the transmission reception control section 15 and denoting of connection to the line from the other system phone 1 are supplied via the phone kind discriminator 16 so as to discriminate whether the other system phone 1 or the telephone set 2 is connected to the line.
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