Abstract: There is disclosed herein a rechargeable battery pack for use with electronic devices, such as electronic flash units used in photography, and wherein the battery pack has a pair of exposed electrical terminals. At least one of the terminals is constructed in the form of a switch such that when the battery pack is removed from its case, the terminal will assume a switched state so as to eliminate any electrical shock hazard. The battery pack comprises rechargeable batteries, a DC/DC converter for converting the relatively low voltage of the rechargeable batteries to the relatively high output voltage of the battery pack, and includes a voltage monitor and limiting circuit which provides voltage regulation and provides a low battery voltage limit during discharge of the rechargeable batteries.

Abstract: There is disclosed herein a battery charger, such as for use with compact low voltage batteries of the type used in consumer electronic products. The charger can sense both voltage and temperature to prevent either an over voltage condition or over temperature condition from damaging the battery being recharged. The charging circuit has fast and slow charge rates, and the circuit oscillates or automatically switches from one rate to the other without requiring the user to manually select or operate a switch for selecting a particular charge rate. The user merely inserts the battery into the charging circuit at a time when it is in the fast mode or slow mode which is indicated by a suitable visual or other indicator device so as to provide a "time selection" of charge rate. The circuit can use a thermal oscillator or an electronic oscillator for switching between the fast and slow rates.

Abstract: There is disclosed herein an electronic flash unit and camera combination wherein the angle of the cone of light emitted by the flash unit is automatically varied as a function of the focal length of the camera lens. In one embodiment the camera lens may be a zoom lens, and means is provided for generating a signal which is a function of the selected focal length position of the lens. This signal is received by a circuit of the electronic flash unit. The electronic flash unit may include a zoom head employing a Fresnel lens or the like for changing the angle of the cone of light emitted by the flash unit. A suitable electromagnetic device, such as a small servo motor and control circuit, responds to the signal indicating the selected focal length of the lens and controls the position of the zoom head of the flash unit. The system is particularly useful with zoom lenses of the type wherein the zooming focal length change is accomplished by moving a zoom ring or "pump" in and out along the axis of the lens.

Abstract: There is disclosed herein a method and an apparatus which provide a tactile indication of the occurrence of a particular event, such as during the operation of a photographic camera, to provide an indication to the operator that a proper exposure condition, like proper focus, aperture or shutter speed, has occurred. For example, and as particularly shown and described herein, a photographic camera includes an autofocus sensing system which senses when a focusing device, such as the focusing ring, of the camera lens has been adjusted for proper focus. When this focus event occurs, an electromagnet operates a brake to prevent the lens focusing device from being turned or operated further, at least momentarily, to thereby provide to the camera operator a tactile indication that the proper focus has been achieved. The electromagnet can be associated with the camera body to engage the focusing device of the lens, or it can be in or within the lens assembly.