| 摘要 |
PURPOSE:To insert audible tone to a call during call without connection change, by adding an audible tone PCM to a call PCM signal at the output side of a time division switch. CONSTITUTION:After an audio PCM signal is stored in a latch register 21, it is written in a memory switch 22 sequentially, and after it is read out at random according to a switch memory 23 and exchanged, it is transmitted to an adder 25 via a PCM signal nonlinear-linear system conversion circuit 24. On the other hand, the audible PCM signal is stored in a latch register 26 on audible tone and selected at an audible tone selector 27 with the control of a selector memory 28, and applied to the adder 25 via the circuit 24. A call PCM signal and the audible tone PCM signal are added at the adder 25. Thus, the audible tone can be inserted to the call tone without connection change. |
