Abstract: A method and apparatus of detecting a tandem link and performing tandem tunneling when a tandem link is detected. The detection of a tandem link includes generating a HAIL and ACK signal where a voice compression unit on one end of the link receives the signals and generates an ACK signal for a voice compression unit on the other end of the link when the HAIL signal is detected. The tandem tunneling prevents the VCUs that comprise the tandem link from decompressing packets received on a network link, adds HDLC header information to the packet to generate HDLC framed packets on the subscriber side, removes HDLC header information from HDLC framed packets received on the subscriber side, and passes the unframed packets to the network side.

Abstract: A method and apparatus of detecting a tandem link and performing tandem tunneling when a tandem link is detected. The detection of a tandem link includes generating a HAIL and ACK signal where a voice compression unit on one end of the link receives the signals and generates an ACK signal for a voice compression unit on the other end of the link when the HAIL signal is detected. The tandem tunneling prevents the VCUs that comprise the tandem link from decompressing packets received on a network link, adds HDLC header information to the packet to generate HDLC framed packets on the subscriber side, removes HDLC header information from HDLC framed packets received on the subscriber side, and passes the unframed packets to the network side.

Abstract: An efficient method and apparatus for determining, recording, and analyzing the phase history of a Line-in signal. The Line-in signal is coupled to a conventional demodulator. I and Q components are output by the conventional demodulator and coupled to an IQ quantizer. The IQ quantizer determines a quadrant on an I/Q plot from the amplitude of each component. A histogram is generated which indicates in which quadrant the Line-in signal was for a first sample, and in which quadrant the Line-in signal was for a second sample, the second sample having been taken immediately after the first sample. From this histogram, the number of times the Line-in signal transitions from one quadrant to another over a predetermined period of time is known.

Abstract: A linear predictive echo canceller is integrated with a RELP vocoder in a two-way communications network, in which a received digitized speech signal synthesized by the RELP vocoder from a residual signal received with linear prediction coefficients is echoed onto a transmit channel and combined with a transmitted digitized speech input signal that is to be analyzed by a RELP vocoder for transmission. The echo canceller cancels the echoed signal from the transmit channel by generating a foreground transmit signal by subtracting a foreground estimate of the echoed signal from the combined signal; and providing the foreground transmit signal on the transmit channel for ananlysis by the RELP vocoder.