Abstract: To actuate an alarm in an automotive vehicle, already present therein, upon theft of a car radio or the like, an electrical switch is formed by a leaf spring (27) secured to a reception frame (11) installed in the vehicle, and insulated therefrom. The leaf spring (24, 24') has a free contact terminal end (27, 27') which, in one embodiment (FIGS. 2, 3), is insulated from contacting the metallic frame when the radio housing (10, 15) is properly secured in the frame by engagement of springy interlock abutments (18) in reception windows (21) in the frame. When properly secured, the free ends (27) of the springs engage a contacting metallic surface (28) on the housing (15) of the radio; upon removal of the housing, the end (27) of the leaf spring (24) rides on an insulated strip and, upon total removal, remains free, so that the switch changes state, thus actuating the alarm; in accordance with another embodiment (FIGS.