US 5,640,685 AGranted

Mobile telephone device wherein an adder supplies a sum of audio and out-of audio band signals to a compressor circuit

AssigneeNEC Corporation

InventorMotoyoshi Komoda

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Abstract

In a mobile telephone device, an adder (17) calculates a sum of (a) an audio signal comprising a talk signal component and a noise component and (b) a generated signal having an out-of audio frequency, as 6 kHz, and a predetermined level and supplies a compressor (21) with the sum as its input signal. The adder and the compressor give a less variable gain to the audio signal of a lower level range than to that of a higher level range. Alternatively, the compressor alone gives the less variable gain to the input signal of the lower level range. A compressed signal is transmitted to a base station as a radio signal and is expanded. For use in a radio communication system of the type in which the generated signal can be given either by the supervisory audible tone or by the reference tone.

Claims15

Dependent claims

A mobile telephone device for producing a radio output signal carrying an audio signal, said mobile telephone device including a compressor circuit for subjecting a circuit input signal to amplitude compression to produce a compressed signal and comprising:

a signal generator for generating a generated signal having a predetermined frequency in an out-of-audio frequency band;
a summing circuit for summing said audio signal and said generated signal into a sum signal;
supply means for supplying said sum signal to said compressor circuit as said circuit input signal;
filter means for removing said generated signal from said compressed signal and for supplying a filtered signal;
and
radio transmitting means for transmitting said filtered signal as said radio output signal;
said audio signal comprising a talk signal component and a noise component having a noise level lower than a maximum allowable level, wherein said circuit input signal is rendered a predetermined level higher by addition of said generated signal to said audio signal, said predetermined level being substantially equal to said maximum allowable level;
and
wherein a gain of said compressor circuit is controlled by said audio signal and said out-of-audio frequency signal.

6 more elements

Dependencies are inferred from the claim text.