This is a circuit that can be used at night in offices, stores, warehouses, etc., to check whether the corporate watchman is on duty. A circuit diagram is a graphical representation of an electrical circuit that employs either simple representations of parts or industry standard symbols. The use of symbols is determined by the audience that is examining the graphic. To operate, it USES an existing phone that is closest to the watchman position (for example, in an office or store).
