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.
A method of displaying alternating transmitting and receiving phases of voice communication in a mobile phone with a display when it is operated in the speakerphone mode includes the steps of comparing the intensity of a received voice signal from a caller with that of a transmitted voice signal, outputting the received voice signal through the speaker of the mobile phone while displaying a visual indication representing the receiving phase on the display if the intensity of the received voice signal is stronger than that of the transmitted voice signal, and sending the transmitted voice signal to the caller while displaying a visual indication representing the transmitting phase on the display if the intensity of the received voice signal is weaker than that of the transmitted voice signal.
In a hands-free handset for a cordless telephone adapted for household use and including a base unit and a handset, the handset includes an automatic receiving and automatic hanging-up control loop, a voice loop and a port switching device. When the user plugs a speaker jack into a speaker socket of the port switching device, the voice loop will switch the voice signal to the automatic receiving and automatic hanging-up control loop, whereby the handset can automatically receive the voice signal or automatically hangs up.
This invention enables freely changing over a handsfree call and a handset call using an information terminal. A call system of this invention includes: a handsfree call microphone and a handsfree call loudspeaker; a first sound device that inputs and outputs a sound to the handsfree call microphone and the handsfree call loudspeaker, and that is included in an information terminal; a handset call microphone and a handset call loudspeaker; a second sound device that inputs and outputs the sound to the handset call microphone and the handset call loudspeaker; a handset connected to the information terminal; and a selection unit for selecting, as each of connection destinations on a transmitting end and a receiving end of a telephone line, at least one of the first sound device and the second device in accordance with a call state and an event, so as to set at least one of the handsfree call microphone and the handset call microphone as an input destination of the sound, and to set at least one of the handsfree call loudspeaker and the handset call loudspeaker as an output destination of the sound.
