Echo suppressor having self-adaptive means

Details Echo suppressor having self-adaptive means Echo suppressor having self-adaptive means

1975-08-22

1977-03-15

Stewart, David L.

1791708, H04B 320

Patent

active

040126030

ABSTRACT:
An echo suppressor employed in systems interconnecting a two-wire circuit with a four-wire circuit for substantially eliminating "talker's echo" and for selectively attenuating the calling party's voice signal when the called party at the two-wire line begins speaking. The signal levels of signals on both paths of the four-wire circuit are measured to extract the maximum values of the signals for succeeding time intervals. The extracted value of the outgoing path signal is divided by the extracted value of the incoming path signal to generate an attenuation factor value. This value is multiplied by the value of the voice signal in the incoming path to generate an estimated leakage level signal. When this level is greater than the signal level in the output path (i.e. when there is no outgoing voice signal) the outgoing path is disconnected to prevent a talker's echo signal from being transmitted thereby. When the signal on the outgoing path is greater than the estimated leakage level signal the outgoing path is not disconnected, and an attenuation circuit in the incoming path is activated to attenuate signals in the incoming path. Delay means are provided to prevent the disconnection of the outgoing path at the initial and terminal ends of a voice signal.

REFERENCES:
patent: 3560669 (1971-02-01), Foulkes
patent: 3823275 (1974-07-01), La Marche
patent: 3896273 (1975-07-01), Fariello
IEEE Transactions on Communications, Dec. 1972, "A Digital Echo Suppressor for Satellite Circuits" by Fariello, pp. 1176-1181.

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