A radio communication system comprise transmitting and receiving stations, a plurality of transmission channels comprising regular and spare channels linking the stations, and a channel monitor for monitoring the status of the respective channels. When the respective transmission channels are in normal conditions, data signal is transmitted by making use of not only the regular channel but also the spare channel. On the other hand, when a failure of any one of the transmission channels is detected by the channel monitor, data signal subject to band compression is transmitted via the non-failed channel. The communication system thus configured makes it possible to effectively utilize a spare channel for effecting high quality signal transmission, while maintaining the essential function of the spare channel, thus providing an improved utilization of transmission channel.