FIELD: physics; radio.
SUBSTANCE: invention relates to radio communication. When a sound presence/absence detector detects a silent interval, a modulated carrier signal is output in the region used for transmitting speech data which are contained in transmission data, having a frame structure and which correspond to the silent interval. In other words, a frequency-shift keying (FSK) modulator initiates output by the transmission circuit of unmodulated carrier signal from the radio communication device to the region used for transmitting speech data corresponding to the silent interval. Meanwhile, a wave signal modulated by FSK with four levels is output in regions different from the silent interval. In the region of channel identification information contained in transmission data with frame structure, there are distinguishing data for absence of modulation to made possible determination of the silent interval, and the distinguishing data enable the communication terminal device at the receiving end to avoid any unstable operations.
EFFECT: communication channel bandwidth reduction and reduced effect on adjacent channels.
6 cl, 7 dwg
