With circuitry configured to obtain the optimum signal-to noise ratio, this 4-place intercom outperformed all other intercoms in tests at noise levels of 115-120 db, making it ideal for homebuilts, ultralights, open-cockpit aircraft, etc. Push to talk intercom or voice activated intercom are available as desired. Separate mic input lines allow the use of different brands of headsets without power conflicts. Compact size (2.5″x 1″) of unit mounts either horizontally or vertically in the tightest panel. Hardware & harness incl. Use of headsets with noise reduction of >24db recommended. FAA TSO approved.