The all new SCI-4 from Sigtronics features dual squelch indicator lights and dual volume and squelch controls to control volume and squelch independently for front and back seats, crew/pilot isolate and pre-wired harness for easy installation. The SCI-4 is RFI and EMI immune and measures only 1"x 2-1/2". Includes all hardware and jacks needed for installation. SCI-S4/S6 Intercoms have the same features as SCI-4/6 Intercoms plus music inputs. 5-year warranty. Made in USA.