A trailer light adapter that is adapted to supply signals to operate the lights of a towed vehicle from modulated signals of a lighting circuit of a towing vehicle, includes at least one input that is adapted to receive a modulated signal from the lighting circuit of the towing vehicle and at least one output that is adapted to supply an output signal to operate a light of the towed vehicle. The adapter further includes a decoder that is adapted to decode a modulated signal and to provide a decoded signal indicative of a desired state of the light of the towed vehicle. The adapter further includes a power circuit that is responsive to the decoded signal and is adapted to supply the output signal to operate the light of the towed vehicle. The adapter may be responsive to a variable voltage modulated signal, a pulse-width modulated signal, or the like.