| 摘要 |
PURPOSE:To form a calling ringing state to be surely listened by a called subscriber without generating noise by allowing a control circuit to count up values corresponding to ringing time after terminating a calling signal and to increase the level of a calling tone in accordance with the increment of the counting value. CONSTITUTION:When a termination detecting circuit 21 in a telephone system 10 detects termination, the control circuit 16 drives a ringing circuit 34C to send a calling ringing tone. The control circuit 16 counts up values corresponding to the ringing time by a ringing counting part 16A and increases the level of the calling ringing tone straight or like steps in accordance with the increment of the counting value. Consequently, a low calling ringing tone is generated in the initial stage of calling, and when no answer is obtained from a called subscriber, the calling ringing tone is gradually increased.
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