Systems and methods insert a modulated signal into audio of a controlled-environment facility resident's side of a call, such as by a controlled-environment communication apparatus, or the like. The same or a different controlled-environment communication apparatus, or the like, may detect the same and/or another modulated signal inserted into the audio of the same and/or another controlled-environment facility resident's side of the call in the audio of an other party's side of the call. The same or a different controlled-environment communication apparatus, or the like, may determine if more than one modulated signal is present in the other call party's side of the call and alert an authority that more than one controlled-environment facility resident is taking part in the call.