| 摘要 |
PURPOSE:To automatically send dial tone to a called subscriber when his line is busy, by providing a calling subscriber class discriminating memory which discriminates the class of calling subscribers and makes recalling possible when a relevant calling subscriber meets line's busy on a called subscriber side and a counter memory for specifying a recalling number of times. CONSTITUTION:When a calling subscriber 1 dials to call up a called subscriber, the received figures are analyzed in an exchange and, when the received numerals are correct and the called side is vacant, the calling subscriber 1 is properly connected with the called side. However, when the received numerals are not correct or the called side is busy, the connection is not performed and busy tone BT is sent to the calling subscriber 1 from a busy tone generator 4. Then direct transition from the state where the busy tone is sent to another state where specifying tone is sent is not made, but whether or not the calling subscriber joins this service is read out and discriminated from a memory. When the calling subscriber joins this service, the busy tone sending state is transferred to a dial tone sending state, and thus, a recallable condition is set. In addition, a counter memory for counting the recalling number of times is provided and, when the recalling number of times exceeds a specified value, the recalling is stopped. |
