US 6,205,217 B1 · Portable telephone set

Abstract

A portable telephone set includes a demodulating circuit which demodulates a signal from a base station to output a demodulated signal. A first signal processing unit amplifies the demodulated signal to output a first amplified signal. An earphone converts the first amplified signal into a sound. A microphone converts a sound into a signal. A second signal processing unit amplifies the signal from the microphone to output a second amplified signal. A modulating circuit modulates the second amplified signal to output a modulated signal. A volume control unit increases the amplification degrees of the signal processing units in accordance with the user's selection. A band limiting circuit limits to the voice band the sound input through the microphone. An S/N determining circuit compares the level of the signal from the microphone and the level of a signal from the band limiting circuit. The volume control unit is rendered inoperative if the S/N determining circuit judges that the ratio of the level of the signal from the microphone to the level of the signal from the band limiting circuit has exceeded a predetermined range during the operation of the volume control unit.

Claims6

Dependent claims

A portable telephone set comprising:

a demodulating circuit for demodulating a signal from a base station to output a demodulated signal;
a first signal processing unit for amplifying the demodulated signal to output a first amplified signal;
an earphone for converting the first amplified signal into a sound;
a microphone for converting a sound into an electric signal;
a second signal processing unit for amplifying the electric signal from said microphone to output a second amplified signal;
a modulating circuit for modulating the second amplified signal to output a modulated signal;
a volume control unit for increasing the amplification degrees of said first and second signal processing units in accordance with the user's selection;
a band limiting circuit for limiting to the voice band the sound input through the microphone;
and
an S/N determining circuit for comparing the level of the signal from said microphone and the level of a signal from said band limiting circuit;
said volume control unit being rendered inoperative if said S/N determining circuit judges that the ratio of the level of the electric signal from said microphone to the level of the signal from said band limiting circuit has exceeded a predetermined range during the operation of said volume control unit.

8 more elements

Dependencies are inferred from the claim text.

Portable telephone set

Life of this patent

Portable telephone set

Life of this patent

Abstract

Claims6