The majority of Christmas lights today use a parallel wiring system. Parallel wiring provides more than one path of electricity for each light bulb to follow. After the current leaves the light bulb it follows two or more paths before returning to the electrical source. The parallel lights have two wires and each light bulb has its own positive and negative wire connection so if one light bulb burns out the rest of the lights remain lighted.

To reduce the risk of overheating the lights, you should replace any burnt out light bulbs promptly. Use the same wattage replacement bulbs as the original strand of lights. All Christmas lights today have fuses to limit the amount of current that will pass through the lights.

Over heating of electrical wires can cause electrical fires.

When using Christmas tree lights, basic precautions should always be followed. Do not use the holiday lights outdoors unless the holiday lights are marked suitable for indoor and/or outdoor use. When outdoor Christmas lights are used in outdoor applications, connect the outdoor Christmas lights to a Residual current device (RCD). If one is not provided, contact a qualified electrician for proper outdoor lights installation.

Christmas lights are not intended for permanent installation or use:

• Do not mount or place Christmas lights near gas or electric heaters, fireplaces, candles or other similar sources of heat.
• Do not puncture the insulation of the Christmas light sets with staples or nails.
• When hanging the Christmas lights do not place the insulated wire on sharp hooks or sharp objects.
• Do not let the Christmas holiday light bulbs rest on the light string supply cord or other electrical wires.
• Unplug the Christmas light bulbs when leaving the house, when retiring for the night, or if the Christmas tree lights are left unattended.
• Your holiday lights are not toys! To avoid risk of fire, burns, personal injury and electric shock the Christmas holiday lights should not be played with or placed where small children can reach the holiday light bulbs.
• To reduce the risk of fire or electrical shock do not mount or support the Christmas tree lights in a manner that can cut or damage the light sets.
• Do not close your doors or windows on the Christmas holiday lights or extension cords as this may damage the wire insulation.
• Do not cover the Christmas holiday light bulbs with cloth, paper or any material that is not part of the light set when in use.
• If your Christmas lights are equipped with push-in type light bulbs, do not twist the holiday light bulbs. Pull the party light bulbs straight out of the light bulb socket.
• If your Christmas tree lights are equipped with threaded screw in holiday light bulbs. Make sure that you do not over tighten the light bulbs causing the protective glass covering to break or crack.
• To reduce the risk of overheating, replace any burned out light bulbs promptly. Use the proper Christmas holiday light bulbs with like volt and wattage replacement light bulbs.
• Always unplug your Christmas holiday lights before installing or replacing the Christmas light bulbs.