Abstract: A multi-channel radio communication system comprising a number of stations for the transmission of speech between the stations, each station transmitting not only the speech signal but also a special so-called busy signal located in a frequency band beyond the speech frequency band, which busy signal informs the remaining stations in the group of which are not occupied by a call to another station that the actual carrier frequency or channel is occupied and cannot be selected for a new connection. According to the invention the busy signal is automatically controlled in amplitude as a function of the instantaneous value of the speech signal and this in such a manner that the envelope of the combination of the speech signal and the busy signal is maintained substantially constant so that as a result of the normal interruptions in a conversation the busy signal will be automatically and repeatedly adjusted to full amplitude.