| 摘要 |
PURPOSE:To eliminate the need for repetition of on-hook/off-hook by providing a called party state identification memory and a timing circuit so as to make a call to other extension without intermission while a handset is hooked off once. CONSTITUTION:In the operation where a called party is busy on the way of connection, for example, if an extension B is busy when an extension A dials the telephone number of the special extension B, logical 1 is stored in an area corresponding to the extension B of a called party state identification memory 25. When a CPU 23 calls the logical 1, a switch SW 30 is controlled to connect an LC 11 and a BTT 22 an to start a TIM 26 and the BTT 22 starts the transmission of a busy tone to the extension A by the command of the TIM 26. When the TIM 26 reaches timeout, it is informed to the CPU 23, which controls the SW 30 to reconnect the LC 11 from the BTT 22 to a REG 21. The caller extension A listens to the busy tone for a prescribed time and then listens to a call tone from the REG 21 so as to attain the dialing for mutual connection with other extension succeedingly.
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