Burglar Alarm.—In order to make a burglar alarm connection with a bell, push buttons or switches may be put in circuit to connect with the[p. 77] windows and doors, and by means of the annunciators you may locate the door or window which has been opened. The simplest form of switch for a window is shown in the following figures:
The base piece (A), which may be of hard rubber or fiber, is ¼ inch thick and 1" × 1½" in size.
At one end is a brass plate (B), with a hole for a wood screw (C), this screw being designed to pass through the plate and also into the window-frame, so as to serve as a means of attaching one of the wires thereto. The inner end of the plate has a hole for a round-headed screw (C') that also goes through the base and into the window-frame. It also passes through the lower end of the heart-shaped metal switch-piece (D)
The upper end of the base has a brass plate (E), also secured to the base and window by a screw (F) at its upper end. The heart-shaped switch is of such length and width at its upper end that when it is swung to the right with one of the lobes projecting past the edge of the window-frame, the other lobe will be out of contact with the plate (E).