Abstract: An inverter circuit having two pairs of transistors, the transistors of each pair thereof being connected in series to alternately and repetitively apply electrical energy to an inductive load such as a fluorescent lamp. A square wave voltage is applied in opposite phase to electrodes of a first transistor of each pair thereof for rendering them alternately in condition for conduction and nonconduction. Each time a first transistor of one pair thereof becomes nonconductive, current in the inductive load reduces and an inductively induced flyback voltage is generated therein, which voltage is applied to the base electrode of the second transistor of the other pair thereof for creating a stored charge which turns on this transistor and keeps it on during the half-cycle, whereby the pairs of transistors are alternately turned on and off for applying alternating current through the load. Rapid discharge circuits are provided for the removal of residual stored charges.

Abstract: A circuit for starting and operating fluorescent lamps from an a-c power source, comprising reactive ballast means connected to ballast the lamps and having a non-linear characteristic for producing harmonics of the power source frequency, and a capacitor and a cathode heating transformer connected in series and connected to receive power from said ballast means and resonant in a frequency range including two or more of said harmonics. A switch may be connected in series with the capacitor and cathode heating transformer for opening the cathode heating circuit when the lamps are operating, to conserve electrical energy.

Abstract: A lamp unit having a housing containing a ballast and provided with a screw base. The base fits over an end of the housing and is attached thereto by a low-cost resin material which, in cooperation with shaped contours on the housing and the base, mechanically locks these parts together.

Abstract: A fluorescent lamp ballast circuit comprising conductors for connection to an electrical power source, and an impedance such as a capacitor connected between one of the conductors and the power source. A positive temperature coefficient resistor may be provided in parallel with the aforesaid impedance.

Abstract: A screw-in fluorescent light unit having two light levels, for use in a 3-way socket. A reactor ballasts the lamp for high light output, and a positive temperature coefficient resistor (thermistor) is added to ballast the lamp for low light output and to facilitate lamp starting at the low light output. The light-level sequence is off-high-low-high-off.

Abstract: Fluorescent lamps are flashed by modulating the lamp operating current during a given half-cycle. The other half-cycle operation is unmodulated, thereby resulting in flashing from full lamp brilliance to substantially one-half lamp brilliance. In one embodiment, the modulating circuitry is placed in the line cord providing power to the lamp. The circuitry includes a gated diode and a resistor placed in parallel with each other. A full wave line cord embodiment employs a diode bridge. In another embodiment, the modulating circuitry is placed across the terminals of a conventional fluorescent lamp starter so that current is bypassed around the starter. With this embodiment of the invention, the discharge on half of the cycle is extinguished, but current flows through the lamp electrodes, thereby keeping them hot enough to emit electrons and prevent life-damaging high cathode fall.

Abstract: A three-terminal thermal switch having a common connector arm biased against a terminal of fusible material. When the terminal is softened or melted by current, the connector arm is released and moves into contact against a second terminal. Positioned in the base of a long-life dual-filament incandescent light bulb, the switch causes one filament to be energized until it burns out, and then connects the other filament to be energized.

Abstract: Lamp modulating circuitry particularly useful for flashing fluorescent lamps in response to music or other audio signals employs an input filter to screen out signals having frequencies less than 20 hertz or greater than 200 hertz. An amplitude demodulator detects the peak amplitude of signals received from the input filter and develops a signal representing the envelope of the low audio frequencies. An automatic gain control compares the instantaneous and average signals derived from the amplitude demodulator and develops an average signal using an output filter. Signals transmitted past the output filter are used by lamp flashing circuitry to cause the output of a fluorescent lamp to be modulated.

Abstract: A screw-in fluorescent light unit having two light levels, for use in a 3-way socket. A reactor ballasts the lamp for high light output, and a resistor is added to ballast the lamp for low light output. A bilateral switch device is connected across the resistor to facilitate lamp starting at the low light output.

Abstract: A screw-in fluorescent light unit having high and low light levels, for use in a 3-way socket. A reactor ballasts the lamp for high light output, and a variable dimming circuit is added to ballast the lamp for variable low light output.

Abstract: A flash lamp array, such as the Flip Flash type, having a plurality of flash lamps positioned in front of a circuit board which has connector terminals thereon. One connector terminal is connected in common to a lead wire of each of a plurality of lamps by means of a metal shield behind the circuit board. The common terminal is connected, by a circuit run, to a lead wire of the nearest lamp; this lead wire and a lead wire of each of the other lamps extend back from the circuit board and contact the shield thus connecting the lead wire and the shield to the common terminal.

Abstract: A variable frequency AC power source drives a gas discharge lamp which is connected in parallel with the capacitance of a series resonant circuit. The polarity of the voltage applied to the resonant circuit is commutated at such times as the rate-of-change of current flow in the resonant circuit is below an adjustable threshold value. The setting of a threshold adjusting circuit determines the brightness of the lamp. The polarity is also commutated at such times as the current flow from the source reaches a predetermined level. Lamp current is thus independently and variably controlled in the variable power mode.

Abstract: A flash lamp array having a plurality of high-voltage flash lamps in front of a reflector unit and a circuit board behind the reflector unit and carrying a plurality of circuit runs of relatively high resistance inexpensive material such as powdered carbon and including a common or "ground" circuit run connected to a lead-in wire of each lamp. The common circuit run is made wider than the other circuit runs, and preferably covers a major portion of the circuit board area. This reduces the possibility of accidental flashing of lamps by electrostatic electricity.

Abstract: A flash lamp array having a plurality of high-voltage flash lamps in front of a reflector unit and a circuit board behind the reflector unit and carrying a plurality of circuit runs of relatively high resistance inexpensive material such as powered carbon and including a common or "ground" circuit run connected to a lead-in wire of each lamp. A shield is positioned behind the circuit board and is connected to the common circuit run near a connector tab at an end of the circuit board. This reduces the possibility of accidental flashing of lamps by electrostatic electricity.

Abstract: A circuit for starting and ballasting a compact high intensity arc discharge lamp, and for preventing failure of the arc discharge. A filament connected in series with the arc lamp provides illumination during arc start-up and functions as a ballast during normal arc operation. An oscillatory starting circuit supplies starting voltage to the arc lamp until an operating arc is established. The circuit includes a "keep-alive" feature which prevents the arc from extinguishing during power fluctuations.

Abstract: A U-shaped discharge lamp, such as a fluorescent lamp, is provided with a starting strip in the form of a pair of conductors respectively extending partially along the legs of the lamp, and an electrical connection is made between the conductors at one end thereof. This electrical connection can consist of or be combined with a support strap. An additional starting strip component can be provided on the U-bend portion of the lamp.

Abstract: A compact lamp unit and associated socket for use in a projection system such as a slide projector, microfilm viewer, and so forth. The lamp unit includes a reflector molded from a plastic material and an electric lamp secured within the reflector. In order to decrease the axial dimension of the reflector and to avoid the use of pin connectors, electrical contacts for the lamp are pressed into recesses formed in the outer surface of the reflector. The reflector includes an opening at its apex through which electrical leads from the lamp extend outwardly of the reflector. The electrical leads are secured to the contacts by being forced into the recesses along with the contacts. This construction technique is fast and simple.The lamp unit also includes a handle to enable a heated lamp unit to be replaced by the user and a guide means to enable the lamp unit to be oriented quickly and accurately upon insertion into the socket.

Abstract: A circuit for starting and ballasting a compact high-intensity arc discharge lamp. A filament connected in series with the arc lamp provides illumination during arc start-up and functions as a ballast during normal arc operation. An oscillatory starting circuit includes a transformer and a frequency-controlling ringing circuit, and applies starting voltage to the arc lamp until an operating arc is established. The circuit includes capacitor means for isolating the starting transformer from the operating path of the arc lamp, and further includes a voltage-doubling starting circuit and also a "keep-alive" feature which prevents the arc from extinguishing during power fluctuations.

Abstract: A compact lamp unit and associated socket for use in a projection system such as a slide projector, microfilm viewer, and so forth. The lamp unit includes a reflector molded from a plastic material and an electric lamp secured within the reflector. In order to decrease the axial dimension of the reflector and to avoid the use of pin connectors, electrical contacts for the lamp are pressed into recesses formed in the outer surface of the reflector. The reflector includes an opening at its apex through which electrical leads from the lamp extend outwardly of the reflector. The electrical leads are secured to the contacts by being forced into the recesses along with the contacts. This construction technique is fast and simple.The lamp unit also includes a handle to enable a heated lamp unit to be replaced by the user and a guide means to enable the lamp unit to be oriented quickly and accurately upon insertion into the socket.

Abstract: An integrally connected fluorescent lamp and ballast unit having an elongated ballast of wire wound around and along an elongated magnetizable core and extending alongside an elongated lamp bulb. The elongated lamp and ballast can be straight, or can be curved. The ballast provides a combined resistive and inductive ballasting impedance for the lamp.