Abstract: A traffic light system (10) with an impedance matching circuit (14) for electrically coupling an optical assembly (12) to a switched AC power supply (26) is described. The impedance matching circuit (14) has a matching transformer (20), a first resistor chain (22) and a second resistor chain (24). Each resistor chain (22,24) has an input and an output. Each of the inputs is common with a respective electrical node of the matching transformer (20). Each of the outputs is common with a respective supply node provided by the primary windings (18a) of an input transformer (18) of the optical assembly (12).