Abstract: Ferromagnetic metal particles the surface layer of which comprises laminatedly covered films of a ferrite compound having a spinel structure of at least one metal selected from cobalt, zinc, manganese, aluminum, chromium, nickel and copper and iron and a preparation process thereof.The particles can be used as a high density magnetic recording medium.

Abstract: A switch device including a casing, a depressible operating member at least partially mounted within the casing and being movable between a protruding position and a depressed position, a cam member movable between an inoperative and operative position in response to the depression of the operating member, the cam member including a cam groove having a loop-like shape, a return spring for urging the cam member toward the inoperative position, an elongated engaging member having one end mounted on the casing and the other end movably disposed in the cam groove, the other end being lockingly engageable in the cam groove to hold the cam member in both inoperative and operative positions, a cushioning member mounted within the casing, the cushioning member being made of a material having elasticity and a high coefficient of friction, and disposed to abuttingly engage the operating member when the operating member is returned from the depressed position to the protruding position, the cushioning member having a ho

Abstract: Disclosed is a process for preparing fine needle-like, ferromagnetic iron compound particles for use in magnetic recording in which needle-like iron oxyhydroxide fine particles prepared by simultaneously co-precipitating or cladding iron compound particles with an element of group II of the Periodic Table and manganese at atomic weight ratios of the element of group II of the Periodic Table and manganese to iron of from 0.001/100 to 10/100 and 0.005/100 to 10/100 respectively are reduced and/or oxidized under heating.

Abstract: An optical apparatus and reproducing machine includes an optical system for viewing a document and for projecting an image thereof onto a moving imaging surface. A plurality of optical elements are arranged along an optical path. The projected image magnification is changed by changing the position of at least two optical elements. An interlock apparatus associated with the magnification changing system is provided for inhibiting the change in position of one of the two optical elements until the other of the two optical elements has completed its change in position, upon the changing of the magnification of the optical system.