An electromagnetic device includes an electromagnet having one electrical coil and an annular member of high permeability having a pair of radially spaced first and second circumferential magnetic resistance portions. The first and second armatures are disposed in opposed relation to the first and second magnetic resistance portions, respectively. At least one of the first and second magnetic resistance portions is interrupted by circumferentially spaced magnetic bridge portions having such a size as to allow a predetermined amount of magnetic flux to pass therethrough to attract the one of the first and second armatures, disposed in opposed relation to the other of the first and second magnetic resistance portions, into contact with the annular member when excitation current of lower magnitude is applied to the coil. When excitation current of higher magnitude is applied to the coil, the magnetic flux passes through the first and second armatures, thereby attracting them into contact with the annular member.