| 摘要 |
PURPOSE:To lessen the load of the caller as well as to decrease the ineffective exchange traffic by memorizing the necessary information by the special instruction of the caller when the called subscriber is busy. CONSTITUTION:When caller A gives a call to called subscriber B when he is busy, central control unit CPE connects caller A to called subscriber busy tone transmission trunk SBTT. When caller A requests the automatic call-back service via hooking and the like, the request is detected by CPE via scanner SCN. And CPE transmits the confirmation signal to caller A and then stores the necessary information including the numbers of the caller and the called subscriber and others into memory MEM. The state of subscriber B is checked every fixed time, and the connection becomes possible between caller A and subscriber B when the line becomes free. |
