Digital attenuator for compressed PCM signals

Details Digital attenuator for compressed PCM signals Digital attenuator for compressed PCM signals

1978-05-26

1980-01-01

Malzahn, David H.

Boots, shoes, and leggings

G06F 739

Patent

active

041819705

ABSTRACT:
A digital attenuator is used in a Digital Echo Suppressor to attenuate a PCM signal. This is done to decrease the influence of echo caused by both long time delay and impedance mismatching at a hybrid coil.
The digital attenuator attenuates the PCM signal which is compressed by .mu. Law, when an attenuation control signal generated in the digital echo suppressor is applied to the digital attenuator. It passes the PCM signal through without attenuating it when the attenuation control signal is not applied.
The attenuator consists of a plurality of pattern shift circuits and an adder or plural number of adders and a selector.
The principle of the attenuation is described hereinafter;
The attenuation quantity is attained from Eq. 1.

REFERENCES:
patent: 3535498 (1970-10-01), Smith, Jr.
patent: 3691359 (1972-09-01), Doll et al.
patent: 3752970 (1973-08-01), Aaron et al.
patent: 3818202 (1974-06-01), Ellison
patent: 3919535 (1975-11-01), Vattvone
patent: 3959639 (1976-05-01), Koethmann

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