Abstract: An electrical contact unit electrically connects a first main member, e.g., a camera housing, with a second main member, e.g., a camera lens, which is mountable on the first main member. The first main member is provided with a contact cradle, which has first electrical contacts, e.g. pins, and a rolling or sliding member. The contact cradle is rotatably mounted on a cradle axle. The second main member is provided with second electrical contacts and a receiving recess. When the second main member is in a first mounting position, it presses against the rolling or sliding member so that the contact cradle assumes a retracted position, in which none of the first electrical contacts are in contact with the second main member.

Abstract: The invention relates to a device at a slide projector for adjusting the slide guide in a plane perpendicular to the optical axis (A--A) of the projector. First fixing means (6-8) are provided to connect a central portion of a first side of the slide guide (2) to the projector. Second and third fixing means (9-15) are located separated from each other on a side of the slide guide (2) opposed to said first side to connect the slide guide to the projector, which second and third fixing means (9-15) are capable to independently of each other adjust and fix the slide guide in the direction of the optical axis (A--A).

Abstract: The invention relates to a device for detachably attaching a lens tube (2) to a lens barrel (1). It is characterized in that the lens barrel inside its forward free edge (5) is provided with peripheral grooves (3) extending in the same plane, the respective bottom of which at the ends (9) of the groove inclined in said plane transforms into the shell surface of the barrel (1), which shell surface tapers conically (6) to the free edge (5) of the barrel. A guide shoulder (4) tapering in wedge-shape thereto is located on the shell surface between two adjacent grooves (3). The tube (2) is provided with radially resilient hooks (11) capable at mounted tube (2) to engage with the grooves (3) of the barrel (1).