Abstract: An apparatus for photochemically curing organic composites used to repair teeth includes a quartz halogen lamp (12) which is activated for a particular length of time by a cycle control circuit (42) which produces a control signal for a preselected time interval. A switching circuit (38) is coupled with the cycle control circuit (42) to interconnect an alternating current source with the quartz halogen lamp (12) at a point in the alternating current cycle when the alternating current crosses a zero voltage level. The control circuit (42) is operably coupled to a time delay circuit (40) which activates the control circuit (42) after a preselected time period after activation of the control circuit (40).

Abstract: An energizing circuit (10) for automatically driving a piezoelectric crystal transducer (Y1) at its resonant frequency includes a resonant circuit (12) of which the transducer (Y1) forms a capacitive element and the secondary winding (80) of a transformer (T2) forms an inductive element. In addition, the piezoelectric crystal itself acts as a series RLC circuit disposed in parallel with the parallel capacitive and inductive elements of the resonant circuit (12). Secondary winding (80) is inductively coupled with a primary winding (74) of the transformer (T2) which forms part of a driving circuit (14). The driving circuit (14) includes a switching circuit (20) connected between a power supply circuit (16) and the resonant circuit (12).