Rollei-werke Franke & Heidecke

Armin Stiller

Stefan Borejko

Joachim Heiland

Two lamps are controlled in that one is off and the other one on or vice versa with fractural transition from one state to the other being controlled by a differential amplifier with integrated, pulse or trigger switch operated Miller integrator. The differential amplifier control circuit elements (transistors, triacs) in separate circuit paths for the lamps. The control is either a direct one (d.c.) or an indirect one through phase shifting of firing pulses in a.c. operated triacs.

Circuit for plural lamp control in slide projectors or the like

An arrangement for supplying a load with controlled current of a predetermined voltage which remains uniform notwithstanding variations in voltage of the alternating current supply, and notwithstanding differences in the frequency of the alternating current supply. A monostable trigger stage of the switch mechanism is connected to a DC voltage which is proportional to the voltage of the alternating current source, and its resistor which is connected with the capacitive coupling of the trigger stage transistors and determines the reset time of the trigger stage, is connected to a constant DC voltage. The mechanism includes a voltage divider, the division ratio of which is variable by means of a frequency recognition circuit.

Arrangement for supplying a load with controlled current from an

Electronic flash apparatus of the general type having exposure-measuring and flash-limiting mechanism comprising a light-sensitive element connected in series with an integrating capacitor and a thyristor, arranged so that when the thyristor becomes conductive, it causes a pulse which interrupts or terminates the flash. In distinction from prior flash apparatus of this same general type, the present apparatus has circuitry in which one plate of the integrating capacitor is connected to the collector of a photo-transistor and the other plate is connected to the control grid of the thyristor and to a higher voltage source, while the emitter of the photo-transistor is connected to a lower voltage source. Other circuit details are disclosed, resulting in a flash unit which is less trouble-prone and easier to adjust than prior flash units of the same general type, and which compensates for the close-up effect so that pictures taken at close range are not over-exposed, as happens so often with many of the prior art flash units.

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Braunschweig, Germany

Armin Stiller