US 6,154,639 A · Handsfree unit

Abstract

The present invention provides a cheap handsfree unit which can prevent the howling phenomenon and reduce the input sound from the loud-speaker into the microphone in both the analog and digital modes. A reception side comprises a signal level adjusting circuit constituted by a switch circuit and attenuators, and a transmission side comprises a signal level adjusting circuit constituted by a switch circuit and attenuators, to introduce the attenuation of 15 dB or 30 dB in response to the analog or digital mode. A voice switch is constituted so that the analog reception signal and the analog transmission signal are rectified respectively by rectifiers, the levels of both signals are compared by a comparator, and either switch or switch having a higher input signal level becomes conductive as a result of the comparison. The attenuation is introduced on the basis of the communication mode, only to either the analog reception signal or analog transmission signal having a smaller signal intensity.

Claims14

Dependent claims

A handsfree unit used in a dual-mode radio communication apparatus for making communication with a base station by selectively employing any one of analog and digital communication modes, for allowing a loud communication to be made,

said handsfree unit comprising:
voice switch means for controlling signal intensity, so that signal intensity of a transmission signal is greater than signal intensity of a reception signal at the time of transmission, and signal intensity of a reception signal is greater than signal intensity of a transmission signal at the time of reception;
and
control amount switching means for increasing the control amount of the signal intensity controlled by said voice switch means when the communication mode of said dual-mode radio communication apparatus is the digital mode, more than the control amount of the signal intensity when the communication mode of said dual-mode radio communication apparatus is the analog mode.

1 more element

A radio communication apparatus for use in a radio system, the apparatus communicating with a base station of the system using one of an analog and a digital communication modes, the apparatus comprising:

determining means for determining which one of the modes the apparatus selects;
first control means for controlling a transmit magnitude of a transmit signal from a microphone and a receive magnitude of a receive signal to a speaker so as to cause the transmit magnitude being much greater than the receive magnitude when the transmit magnitude is greater than the receive magnitude and so as to cause the receive magnitude being much greater than the transmit magnitude when the receive magnitude is greater than the transmit magnitude;
and
second control means responsive to the determining means for causing the controlling quantity of the transmit and receive magnitudes in the digital mode being greater than those in the analog mode.

1 more element

Dependencies are inferred from the claim text.

Handsfree unit

Life of this patent

Handsfree unit

Life of this patent

Abstract

Claims14