| 摘要 |
PURPOSE:To surely lock a talking by illegal operation by applying self-check to a fault and inhibiting at least a charged talking accordingly if the fault takes place in a forced cut-off circuit and the forced cut-off is disabled. CONSTITUTION:Means 2, 3 sending a talking loop hit signal to a forced cut-off circuit 4 immediately after a talking loop is closed, detection means 1, 5 detecting the state of the talking loop and a talking control means 7 inhibiting at least the charged talking by the detection output of the detection means 5 during the transmission of the talking loop momentary interruption signal are provided. Thus, after the talking loop at transmission is closed, the self- diagnosis of the forced cut-off circuit 4 is applied immediately and when the closed state is shown in the detected output, at least the charged call is inhibited. Thus, the illegal operation such as talking by the repetition of toll call by a local talking charge is prevented.
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