Sidetone is the sound of a user’s voice in his/her own headset earcup. This allows the user to speak in a natural manner when communicating verbally. It can optionally enabled or disabled in the SimPTT program. If enabled, it may be used as an indication that the microphone is live (hot) or that the user is transmitting audio. The Simradios products produce zero-latency sidetone, meaning there is no perceptible delay for the user.