Abstract: A duplex voice communication radio transmitter-receiver according to the present invention is provided with a low-pass filter arranged before a time compressing device in a transmitter section for cutting off a higher frequency portion of the band of a voice signal thus to decreasing the maximum modulation frequency of the same to less than a half so that it can be operated with the use of an assigned, single frequency transmission radio wave of which frequency band is legally limited, improved in the utilization of frequencies, minimized in the delay of communication signals, and enhanced in the articulation and intelligibility of a reproduced voice sound.