This Beta has an MPX plug and switch. Set it to ON when recording using an external FM receiver (tuner) that does not have filtering. If the FM tuner has an MPX filter setting, set this switch to OFF. This switch only affects recording. It removes the 19 kHz pilot tone and the 38 kHz subcarrier of an FM stereo broadcast that can cause harmonics at these frequencies and produce a very annoying whistling. Consult the manual for the external device being used. Click on the MLV-1100 for more about the MPX processor. ©Misterßetamax go to homepage