The Clarity SWM series mixer-amplifiers mix and control up to three inputs. Input one accommodates either a low impedance balanced microphone or 600 ohm tel line audio input. Input two allows the use of a low impedance balanced microphone or a high impedance auxiliary input. Input three is used with a high impedance input.All three models are wall mountable and include individual input controls along with bass, treble, master gain, and tone level controls. LED indicators are provided to show power "ON" and clipping. Automatic Level Control is provided on the Tel line input. The mixer-amplifiers are equipped with two types of tone signaling, warble and single tone. These tones are activated by contact closures. In the event both contacts close simultaneously, the single tone will override the warble tone.