PURPOSE: To prevent the deterioration of the voice quality owing to the no-hook of the subscriber, by monitoring the channels of the conference participants and then excluding the channel having input PCM code showing the DC signal, if detected, and then returning the channel to the conference when no DC signal exists any more.
CONSTITUTION: The connection is given among the conference telephones by means of the PCM time-division telephone exchange. And the comparison is given through comparator 22 between plural number of channels in the No. N frame counted from input 20 of the digital conference telephone circuit and each PCM code of plural number of channels in the No. N-1 frame delivered from 256-bit shift register 21. The result of this comparison is memorized temporarily in 32-bit shift registers 23∼26 each. And based on the comparison result of comparator 22 and the comparison results of M frequencies among plural number of channels of N-i frame and N-i-1 frame which are memorized in registers 23∼26, the PCM code is always detected through AND gate 27 and then applied to NAND gate 30. Thus only the PCM code having no coincidence exists for the channel to be given to expander 2.
| JPWO2012111251 | Group generator |
| JP2010074494 | CONFERENCE SUPPORT DEVICE |
KOBAYASHI YUKIO
MASUDA NOBUYUKI
