Abstract: The invention relates to a bipolar plate (7) for an electrochemical cell (1), said bipolar plate comprising at least one first monopolar plate (13) having a first bead (15) and a second monopolar plate (17) having a second bead (19), the first bead (15) and the second bead (19) being arranged opposite one another and forming a channel (21), the first bead (15) and the second bead (19) each comprising a central base surface (23) and at least two inclined surfaces (24) and the first bead (15) and/or the second bead (19) comprising at least one outer base surface (25), and wherein the at least one outer base surface (25) and/or the central base surface (23) have at least one opening (27) for the passage of at least one medium (29). The invention also relates to an arrangement of electrochemical cells (1) and a method for operating an arrangement of electrochemical cells (1).

Abstract: A camera with a varifocal objective is equipped with an indicator which signals the existence of a condition unsuitable for the taking of pictures because of the risk of blurring, especially when the camera is held by hand, as where a large focal length is chosen together with a long exposure time. The indicator is overridden upon reduction of the risk by certain precautionary measures, including the use of a self-timer which generally involves placement of the camera on a stable support.

Abstract: A camera of variable focal length is equipped with an indicator which signals the existence of a condition unsuitable for the taking of pictures because of the risk of blurring. The indicator is controlled by a sensing circuit taking into account such parameters as focal length, exposure time and, possibly, the steadiness of the camera support.

Abstract: A device for determining the position of at least two objects movable relative to each other preferably in a pre-set counter train which includes operatively associated optical elements supported on the objects together with a transmitter for emitting a directional beam such as an electromagnetic wave transmitter for producing an electromagnetic beam and a receiver onto which the beam is directed, the beam being directed in a unidirectional path onto the receiver when the optical elements are in a predetermined aligned position and being deflected from such path to an extent corresponding to the relative position of the objects and the optical elements supported thereon to provide an output from the receiver responsive to relative position of the objects.