A lighting system, comprising: ∘ a first light source (LED string 1); ∘ a first power supply connector configured to receive power for the first light source (LED String 1) from a first DC power supply via a power line; ∘ a first modulation element operatively coupled to the first light source (LED string 1); and ∘ a first processor (μC B) configured to use the first modulation element to modulate one of DC current flow through the first modulation element or DC voltage drop across the first light source (LED string 1), thereby providing a first power line communication signal, which is outgoing on the power line to the first DC power supply; ∘ a first switch configured to control the in-circuit presence of the first modulation element in response to a first modulation control signal provided by the first processor (μC B), so as to modulate one of DC current flow through the first modulation element or DC voltage drop across the first light source (LED string 1), thereby providing the first power line communication signal, characterised in that: ∘ the first modulation element is electrically connected in series with the first light source (LED string 1) and the first switch is electrically connected in parallel to the first modulation element, such that the DC voltage drop across the first light source (LED string 1) is modulated in response to the first modulation control signal, or ∘ the first modulation element is electrically connected in parallel with the first light source (LED string 1) and the first switch is electrically connected in series to the first modulation element, such that the DC current flow through the first modulation element is modulated in response to the first modulation control signal. ∘ a first light source (LED string 1); ∘ a first power supply connector configured to receive power for the first light source (LED String 1) from a first DC power supply via a power line; ∘ a first modulation element operatively coupled to the first light source (LED string 1); and ∘ a first processor (μC B) configured to use the first modulation element to modulate one of DC current flow through the first modulation element or DC voltage drop across the first light source (LED string 1), thereby providing a first power line communication signal, which is outgoing on the power line to the first DC power supply; ∘ a first switch configured to control the in-circuit presence of the first modulation element in response to a first modulation control signal provided by the first processor (μC B), so as to modulate one of DC current flow through the first modulation element or DC voltage drop across the first light source (LED string 1), thereby providing the first power line communication signal, ∘ the first modulation element is electrically connected in series with the first light source (LED string 1) and the first switch is electrically connected in parallel to the first modulation element, such that the DC voltage drop across the first light source (LED string 1) is modulated in response to the first modulation control signal, or ∘ the first modulation element is electrically connected in parallel with the first light source (LED string 1) and the first switch is electrically connected in series to the first modulation element, such that the DC current flow through the first modulation element is modulated in response to the first modulation control signal.