Speakerphone using digitally compressed audio to detect acoustic

Telephonic communications – Having light wave or ultrasonic link for speech or paging... – Including fiber optic link within telephone network

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379 63, 379390, 370 32, H04Q 704, H04M 100, H04M 1100

Patent

active

048436216

ABSTRACT:
A mobile radiotelephone (120) includes a microcomputer (220), speakerphone control circuitry (106) and mobile radio (112). In the transmit voice path, speakerphone control circuitry (106) includes switch (201), variable gain amplifier (202), compressor amplifier (203), switch (204), variable gain amplifier (205), and two registers (212-213). In the receive voice path, speakerphone control circuitry (106) includes variable gain amplifier (232), expander amplifier (233), switch (234), variable gain amplifier (235), switch (236) and two registers (216-217). Speakerphone control circuitry (106) also includes rectifier/filter (224), a companding analog-to-digital (A/D) converter (225), two latches (218-219), rectifier/filter (226) and two registers (214-215). Microcomputer (220) accesses registers (212-217) by means of a data bus (222) including address, control and data lines. Microcomputer (220) utilizes digital samples from A/D converter (225) to dynamically detect acoustic feedback and to continuously generate and store in its memory an envelope signal and a valley signal for the transmit and receive voice paths for controlling voice path gain switching. In order to determine when to switch gain between the voice paths, microcomputer (220) compares the envelope signal to the valley signal to detect the presence of voice signals and, if the voice signals are detected for a pre-selected time, the gain of the path in which voice signals have been detected is increased and the gain of the other path is decreased.

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