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. In an alternate embodiment, a substrate that has a depression of an undercut or a notch in a top surface of the substrate is utilized. The transparent substrate does not absorb the emitted light, thereby the light emitting efficiency is increased by as much as double, and thus the performance of opto-electronic devices is improved. Typically, sensors of the invention communicate by an RF transmitter or transceiver.