Point Source Audio CM-I3-PH Intercom Headset With 3.5mm PlugThe Point Source Audio CM i3 PH Intercom Headset with 3. 5mm Plug is a modular intercom headset designed for concert venues, front of house operations, multimedia production, and other professional trades that rely on convenient two way communication systems. The headset allows for three different listening modes. Instead of having to remove the entire headset to check sounds in the environment, the user can simply remove one or both of the earphones.