1. In a communication device having a speech input device and a voice output device in proximity to one another wherein an output from the voice output device may be feedback to the speech input device, a method of applying loss insertion into the communication device to prevent feedback oscillations/ acoustic instability between the speech input device and the voice output device, comprising the steps of: applying an identification mark to output from the voice output device; introducing insertion loss in the inactive path of the speech input device and voice output device based on their relative signal levels in order to reduce the feedback oscillations.