... Internal voltage-controlled oscillator, Three working modes MCH-2893A Speaker Tester, impedance test ModelMCH2893ATest parameterImpedance /Z/ ZZero ... clearing 0Short-circuit zero clearing 0Range mode Automatic, manual ,Test portTwo ports 2Display LED display, frequency 4 digits ... notice. MCH Speaker Impedance Tester,MCH-2893A Speak tester,400Hz,1KHz fixed freq,20Hz-4Khz manual adjusting, 50Hz- ...