Abstract: A full duplex talking audio circuit uses a single transducer ZT which, even when various characteristics including the strength of a transmission signal change from moment to moment, enables the adequate operation of an echo canceling function and sufficiently compensates for the deterioration of the frequency characteristics of the transmission signal due to the acoustic transfer characteristics of the human body.

Abstract: Embodiments of the invention provide a small and economical two-way communications device that has both an excellent echo-cancellation function that substantially suppresses echoes over the entire frequency range and an excellent voice-operated exchange function that provides natural switching of conversation sounds while protecting against unnatural disconnection or echoes during conversation, even when a reception signal and a transmission signal are superimposed in a single transducer.

Abstract: A base unit and a handset comprise a wireless part, a control part, and a transmission (151) and reception part (150), respectively. Communications are switched by either of the two ways: PTT switching and tone generation in the base unit, and tone detection in the handset or PTT switching in the base unit, and voice detection in the handset. It is preferable that the transmission (151) and reception (150) part of the handset includes a single transducer type headphone. It is also preferable that photo-coupler (41, 43) and a photo-switch (42) are provided at connection point of signal paths between the transmission (151) and reception part (150), the control part, and between the control part and the wireless part.

Abstract: A base unit and a handset comprise a wireless part, a control part, and a transmission (151) and reception part (150), respectively. Communications are switched by either of the two ways: PT switching and tone generation in the base unit, and tone detection in the handset or PTT switching in the base unit, and voice detection in the handset. It is preferable that the transmission (151) and reception (150) part of the handset includes a single transducer type headphone. It is also preferable that photo-coupler (41, 43) and a photo-switch (42) are provided at connection point of signal paths between the transmission (151) and reception part (150), the control part, and between the control part and the wireless part.

Abstract: A full duplex talking audio circuit uses a single transducer ZT which, even when various characteristics including the strength of a transmission signal change from moment to moment, enables the adequate operation of an echo canceling function and sufficiently compensates for the deterioration of the frequency characteristics of the transmission signal due to the acoustic transfer characteristics of the human body.

Abstract: Embodiments of the invention provide a small and economical two-way communications device that has both an excellent echo-cancellation function that substantially suppresses echoes over the entire frequency range and an excellent voice-operated exchange function that provides natural switching of conversation sounds while protecting against unnatural disconnection or echoes during conversation, even when a reception signal and a transmission signal are superimposed in a single transducer.

Abstract: A headset includes two earpieces. One earpiece acts as a microphone, and the other earpiece acts as an earphone. Isolated from background noise and vibrations due to bone conduction, the microphone earpieces convert voice sounds from the air column in the external ear canal into electrical signals. Other embodiments of the invention address feedback problems and achieve improved performance relative to existing full duplex communication devices. In another embodiment of the invention a headset includes a band having opposite ends that extend in a forward direction from the two earpieces. The band then either extends downwardly or backwards.