A coded light transmission and reception circuit and transmission and reception method use signals to indicate the start and end of a coded light transmission window. Data is modulated onto the current waveform during the transmission window. Each data peak value during said transmission window exceeds an average current in the transmission window (which is used as the decision level) and each valley value during said transmission window is below the average current. In this way, a coded light output can be generated in which the overall decision current varies significantly, but the coded light signal can still be decoded reliably. The average level can be cacluated in the receiver and used for demodulating.
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