Abstract: A signal transmission method for transmitting a signal between a regulated power supply unit that operates and controls a high intensity discharge lamp and a setting unit that gives various kinds of commands to the regulated power supply unit is provided. The method includes providing the regulated power supply unit with a first communication controller; providing the setting unit with a second communication controller; providing a pair of signal lines.

Abstract: A lighting-drive device includes: a lighting-drive circuit configured to drive a lamp for lighting of the lamp; an activation circuit configured to produce an activation voltage to be applied to the lamp in order to start lighting of the lamp; and an activation operation detector configured to be provided with a sensing member for sensing an induced voltage and output an operation state notification signal depending on a state of the induced voltage. The sensing member is provided on a circuit substrate on which the activation circuit is formed in such a manner as to be allowed to sense the induced voltage. The activation current flows in response to the activation voltage produced by the activation circuit. The operation state notification signal indicates whether or not the activation circuit has operated normally. The lighting-drive circuit, the activation circuit and the activation operation detector are integrated into one single component.

Abstract: A signal transmission method for transmitting a signal between a regulated power supply unit that operates and controls a high intensity discharge lamp and a setting unit that gives various kinds of commands to the regulated power supply unit is provided. The method includes providing the regulated power supply unit with a first communication controller; providing the setting unit with a second communication controller; providing a pair of signal lines.