Abstract: A lighting system (1) comprises a plurality of high intensity discharge lamps (9, 39, 6) and an electronic control (2) having a power input (4), an alternating current power output regulator (22), and an alternating power output (3) having an output frequency arranged to be variable within an output frequency range, the output having a first and a second output line. The lamps are connected in series with each other so that the first line is connected to the first electrode (11) of the first of the lamps, the second electrode (12) of the first of the lamps is connected to the first electrode (41) of the next lamp in the series, the second electrode (13) of the final lamp in the series being connected to the second output line. The lamps have an acoustic resonant frequency range and the output frequency range of the control is arranged to be above the acoustic resonant frequency range.

Abstract: A lighting system (1) having a high intensity discharge lamp (16) mounted replaceably in a holder (25) which connects to an electronic control (8) which includes a variable frequency generator (10), a joint operating circuit extends from the lamp to the control; the control is arranged to sweep over a predetermined range of frequencies to produce by means of a resonant circuit which includes in the circuit (22) capacitance (12, 13, 21) which is at least partly in or on the lamp. Removal of the lamp from the system prevents the production of the resonant high voltage ensuring improved safety.

Abstract: An electronic control (1) for a discharge lamp (D), which is arranged to be connected to a source of alternating current (L,N), having a source frequency, the control having a first and second terminal (J,K) for supplying an electrical power output to operate the lamp; a capacitor (T) is in series with the first terminal, having a capacitance sufficiently small to limit a current flow from the first terminal at the source frequency of less than 30 mA.

Abstract: A lighting system (1) having a high intensity discharge lamp (16) and an electronic ballast having a variable frequency generator (10) which is arranged to vary the frequency of the ballast output over a range of frequencies having a minimum frequency of 400 kHz; a reactance is included in a joint operating circuit (22) in and between the ballast generator (10) and lamp (16) such that the circuit resonate to provide a starting voltage for the lamp at or above the minimum frequency. The arrangement inhibits lamp flickering and improves overall lamp and system efficiency.