In a handsfree telephone system of the type described in our application No. 584,579, filed in the U.S. on Feb. 29, 1984, the method used to avoid howling due to feedback from the loudspeaker to the microphone is to increase the attenuation to speech in the quiescent direction as compared with that in the active direction. This involves monitoring successive speech samples in the two directions with each sample compared with a preset threshold, which also takes account of the system's noise leve...

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 ...

A handsfree communication apparatus utilizing a plurality of microphones to allow simultaneous communication by a plurality of persons. The plurality of microphones are separately provided apart from one another. An amplifier section (or a noise canceller) includes a plurality of operational amplifiers for signal amplification individually corresponding to the plurality of microphones, and differential amplifier circuit for executing a differential amplification. Through the differential amplifi...

A universal handsfree set seat on which various types of mobile phones can be placed. The dimension of the rest section of the handsfree set seat is adjustable according to the volume of the mobile phone. The universal handsfree set seat includes a seat body, a clamping mechanism and a twin-head connecting plug for receiving and connecting with various telecommunication peripheral equipment.

A handsfree mobile telephone rack for holding any of a variety of mobile telephones permitting a user to send a message by a mobile telephone with both hands free, comprising a power socket connected to a power supply by a power cord, a power switch, a volume control, and two loudspeaker circuits, wherein the two loudspeaker circuits each comprised a microphone and a loudspeaker with the output volume thereof regulated by the volume control; the two loudspeaker circuits include one for transmitt...

A handsfree or loudspeaking telephone circuit employing loudest speaker comparison for controlling the direction of transmission of speech signals. The circuit employs the speech network for the handset to provide gain and hybrid functions. The circuit contains logic for controlling the switching between handset operation, handsfree operation and call announcing operation.

To amplify low frequencies emitted in handsfree mode by a multifunction earpiece (earpiece, loudspeaker, buzzer) of a telephone handset, the earpiece being tolerant to leaks in a discreet mode of operation, a tube projects into a cavity in the casing of the handset, around an aperture through which the cavity communicates with the exterior of the casing. The handset thus includes a multifunction earpiece that is tolerant of leaks in a discreet mode of operation and provides good sound quality in...

A handsfree communication terminal apparatus includes a transit switch being controllable for passing signals from a microphone to a transmission interface, during a transmit mode of operation, and a receive switch being controllable for passing signals from the transmission interface to a loudspeaker, during a receive mode of operation. A transmit signal processing circuit followed by a converter circuit generate transmit binary signal assertions in response to syllable-like characteristics in ...

In a loudspeaking telephone arrangement, there are separate channels for outgoing speech (A-Tx) and incoming speech (A-Rx), and the channels are sampled at intervals. The results of these samplings, which represent the amplitudes of the speech in those channels are each compared by a microprocessor with a preset threshold. The background noise level is also sampled and the result used to adjust the speech channel threshold. Each channel has an attenuator, and that is adjusted so that attenuation...

A handsfree car mounting kit for a mobile telephone (6) coupled to a head-set (4) via a Bluetooth radio module consists of a passive communications unit (1), which has a loudspeaker and a microphone (5), optionally coupled to an amplifier, arranged in a cabinet which has a bearing or a holder on its outer side in which the headset (4) may be placed and connected electrically to the communications unit. Further, the cabinet is provided with a plug terminal for a 12 volts socket terminal (3), such...