| 摘要 |
A digital conference circuit for a digital telephone switching network is provided, connected between a receive TDM (time division multiplex) bus carrying PCM (pulse code modulation) words from the conferees to the conference circuit and a transmit TDM bus carrying PCM words from the conference circuit to the conferees. For a conference involving N conferees, N-1 shift registers serially interconnected are employed. As each PCM word, in a distinct time slot on the receive TDM bus, reaches the conference circuit it is entered into the first shift register in the series. The PCM words already stored in the shift registers are "shifted" along the series connection of shift registers by one register each time a new PCM word is entered in the first register, with the PCM word previously stored in the final shift register simply being "lost." Circuitry within the conference circuit monitors the binary value of the PCM words stored in the registers and during the time slot that one PCM word is being received from a conferee, the PCM word previously stored in one of the N-1 registers that has the largest absolute binary value is output on the transmit TDM bus and it is received by the conferee who is "talking" during that same time slot (referenced to the conference circuit). With such a conference circuit a conferee never hears himself since the selection of whom he shall hear is made from the PCM words of all the other (i.e. N-1) conferees. |
