Complete Communications Engineering

A full-duplex speakerphone or intercom device digitizes the signal coming out of its speaker. It then edits this info out of the signal it’s transmitting using a built-in digital processor. This eliminates echo effect and more importantly, does away with the on-off mic/speaker dilemma. Full-duplex devices do all of this virtually instantaneously.

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Full-duplex conversation, where both transmit and receive channels are active simultaneously, is the conversation. Full duplex for hands-free communications is achieved using Echo Cancellation. Echo Cancellation reduces overall loop gain and the acoustic coupling between speaker and microphone. This coupling reduction prevents the annoying effect of hearing one’s own delayed speech, which is worsened when there is delay in the system, such as vocoder delay.

Half-duplex devices let you send and receive, but only one-way at a time. If you’ve ever used a walkie-talkie, then you know what half-duplex conversations sound like. You have to push the TALK button to send your message. But as long as you are holding the TALK key, you can’t hear what anyone else is saying. You must release the button to receive.

This software can be combined with VOCAL’s VoIPTelephonyVoice CodecData Modem, and/or Fax Modem modules.

The line interface may be an analog front end (codec and DAA) or a digital interface such as T1/E1, Switched 56, and ISDN.



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