An all-digital audioconference system

An all-digital audioconference bridge based on a four-wire network connection has been implemented. The audioconference bridge is implemented as a wire-wrap plug-in board to a digital exchange on a 2.048 Mb/s 32-channel PCM (pulse code modulation) link. The digital system is superior to the existing analog audioconference systems both in terms of setup time and quality of transmission. A general bridge has been designed which can alternate between different meeting strategies in order to compare the performances of the strategies under the same conditions of transmission. New meeting strategies can easily be implemented because of program controlled switching. Subjective tests have established that the quality of transmission can be improved noticeably by using the two instant speakers algorithm instead of the classical addition or instant speaker algorithms. By using a `meet-me´ setup system a subscriber can call the bridge with an ordinary telephone, thus speeding up the startup procedure and distributing efforts and costs among the participants. This procedure is much easier than the operator handled startup as found in previous systems