An inverter for providing power to a lamp coupled to a power supply and a lamp circuit. The inverter can selectively provide the lamp circuit with AC voltages of two different frequencies. The inverter includes: a first switch for passing a DC voltage; a first and second oscillating circuit coupled to the first switch that receives DC voltage and respectively generates a first AC voltage having a first frequency and a second AC voltage having a second frequency; and a transformer coupled to the first oscillating circuit and the second oscillator for transforming the first AC voltage provided by the first oscillating circuit or the second AC voltage provided by the second oscillator into a third AC voltage and passing the third AC voltage to the lamp circuit. The first switch serves to selectively pass the DC voltage to the first oscillating circuit or the second oscillating circuit.