Abstract: A paging system for a PBX comprises an amplifier/speaker module adapted to remain coupled across the Ring and Tip lines of a given phase of the PBX. The module responds to audio signals sent through such lines when the conventional polarity of same are reversed and a DC operating bias is applied thereto. The audio signals are superimposed on the DC bias. A relay controls the polarity of the Ring and Tip lines and when activated, reverses the polarity of such lines whereupon the module amplifies the audio signals and applies them to a speaker. The module includes circuitry to prevent the amplifier from operating when the relay is de-energized and Ring and Tip lines are of conventional polarity.