Left side is line voltage input plug in. Lines with ground connections is picturing house outlet plug in box with duplex type plug in allowing series wiring of outlet. Note 7.5 bulbs light but working higher wattage lights below do not light. This can be used to check for shorts or breaks in wiring by twisting and pulling power cords and control current levels. Heavy duty appliances may need bulb larger than 7.5 watts.
