Speakerphone using digitally compressed audio to control voice p

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

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455 72, 370 32, 379 63, 381106, H04Q 704

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047410183

ABSTRACT:
A mobile radiotelephone (120) includes a microcomputer (220), speakerphone control circuitry (106) and mobile radio (112). Mobile radio (112) includes a transmitter (242), receiver (244) and a duplexer (243) for coupling the transmitter (242) and receiver (243) to the mobile antenna. 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 continuously generate and store in its memory an envelope signal and a valley signal for the transmit and receive voice paths. 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.

REFERENCES:
patent: 4123711 (1978-10-01), Chow
patent: 4378603 (1983-03-01), Eastmond
patent: 4400584 (1983-08-01), Vilmur
patent: 4550426 (1985-10-01), Gillig et al.
patent: 4560840 (1985-12-01), Hansen
patent: 4677645 (1987-06-01), Kaniwa et al.

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