Specifically designed to work with all Barcus-Berry electret mic systems. Features external bass, treble and volume frequency controls to allow a wide range of adjustments. Includes a belt clip for unrestricted movement.Input (EQ Flat): Input Interface = RCA unbalanced Input Impedance = 2.2 Meg Ohms Maximum Input Level = 2.0 vrms Output (EQ Flat, Volume Max): Interface = 1/4