| 摘要 |
PURPOSE:To operate normally even when a telephone line of a caller side is not subject to current conversion by judging that a called party is replied in case no ring back tone comes from the called party. CONSTITUTION:In lifting up a handset of a telephone set 16 for exclusive use of automatic call, a hook switch 20 is turned on, a telephone set 14 is disconnected from lines 12a, 12b by the action of a relay 34 or the like, an automatic call circuit 32 is operated to call the called party. When it is detected that the interval of call tones goes to a prescribed value or over by the operation of a call tone detection circuit 56 and relays 60, 62, a reply message is sent from a reply message circuit 72 to lines 12a, 12b, then the telephone set 16 is connected to the lines 12a, 12b. Then, even when no current conversion is applied to the lines 12a, 12b by the reply of the called part such as a collect call, the reply of the called party is detected and normal operation is attained.
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