| 摘要 |
Disclosed is a circuit and method that eliminates the problem of voice echo created by the use of simultaneous voice and data (SVD) modems in a remote office application. In the instant invention, a voice signal originates in a remote office telephone and is modulated with a data signal and sent from a first SVD modem to a second SVD modem, where it is demodulated and then routed from the second SVD modem back into the switching network to a second telephone where a voice echo signal may be created by existing hybrid transformers. This echo signal will follow the return path of the voice signal to the second SVD modem where it is modulated with a data signal, sent back to the first SVD modem, demodulated, and then routed back to the remote telephone. The echo and voice signal is thus delayed by the modulation and demodulation of the voice and data signals in both SVD modems by a time period of greater than thirty-five milliseconds. The result is an intolerable and disruptive echo signal that is perceived by the person speaking in the remote which is eliminated by the introduction of voice echo cancellation in the circuit.
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