Image Number 12 for United States Patent #7826805.
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.