The invention may be used for communication between a plurality of users in a frequency modulated radio communication system having a continuous tone controlled squelch system, CTCSS. An audio frequency channel and multiple CTCSS sub-channels may be selected for a carrier signal transmission between multiple users. A distinct one of the CTCSS sub-channels may be assigned to each user. The carrier signal may be transmitted with the audio frequency channel and one of the CTCSS sub-channels. The audio frequency channel may be monitored to detect the carrier signal. The detected signal may be monitored to detect a CTCSS sub-channel signal. If a selected CTCSS sub-channel signal may be detected, an audio output device may be activated.