| 摘要 |
PURPOSE:To superpose a sound code economically by superposing plural sound signals one over another without installing plural mixing trunks in a digital exchange. CONSTITUTION:The digital exchange consists of a multiplexing circuit MPX, channel memory SPM, mixing memory MXM, separating circuit DMPX, control part SMC, switch information storage part REG, signal reception and distribution part SRD, and central controller CC. When in-call incoming display service, interrupt call service, conference telephone service, etc., are offered through the digital exchange, a sound signal such as an incoming display tone is stored in a specific address of the memory SPM and a subscriber's voice and various signal tones are superposed in the storage part REG and stored after time slot replacement. This stored signal is sent out from a down highway to each subscriber through the circuit DPMX by using a specific time slot. Thus, the means for superposing the sound signal is provided in a time-division switch, so the need for a mixing trunk is eliminated. |
