The lumen (symbol: lm) is the unit of the International System of Units to measure the luminous flux, a measure of the light power emitted by the source. The luminous flux of radiant flux difference that the former provides the variable sensitivity of the eye to different wavelengths of light and the latter involves all electromagnetic radiation emitted by the source according Wien law and Stefan-Boltzmann regardless of whether such radiation is visible or not. 1 lm = 1 cd. sr = 1 lx. m2

VDC would be the abbreviation for Volt Direct Current which translated would volts direct current. The idea of ??this type is unidirectional current to the load. Direct current is normally produced by batteries, thermocouples, solar cells and a dynamo electric machine type. The direct current can flow in conductors such as wires, but may also flow through semiconductors, insulators ... In the image: 1 - current per pulse 2 - Direct Current (DC) 3 - Alternating Current (AC) 4 - Variable Current

The socket is the part that allows connecting the bulb to the socket. There is a wide selection of bushings for different types of bulbs. The nomenclature for each type includes 1 or more letters (type of lampholder), followed by 1 or more numbers (diameter of lampholder).
Example: The bush E27 would correspond to the type of thread E (Edison) of 27mm in diameter.

• E12: Diameter of 12mm, this is a tamYear smaller than the most commonly used standard E27.
• E14: It is the second most common cap, only varies a little of the E27, with a diameter of 14 to 17 mm. It is normally used for bulbs or lamps.
• E27: This is the most common cap. It has a thick cup shape with thread to be able to adapt to the connector. It measures 27mm wide.
• E40: Has a diameter of 40 mm, it is the largest thread of this tIpo.
• G4: With a distance between pins of 4.0 mm. It is a type of cap that is frequently used in appliqués, ceiling lamps and hanging lamps.
• G5.3: With a distance between pins of 5.33 mm. The GU 5.3 socket format is a format widely used in small led floodlights with transformer. Usually used in halogen lamps and dichroic halogens.
• GY6.35: With a distance between pins of 6.35 mm, trOf a model similar to the previous one.
• G9: With a ditancia between pins of 9,0 mm. Usually used for ceiling lamps and hanging lamps.
• G13: With a distance between pins of 12,7 mm. It is used in fluorescent tubes.
• GX53: With distance between pins of 53 mm. Its most common use is the installation in light bulbs to illuminate furniture or unusual places. It does not need transformer.
• GU10: With a distance between10 mm pins. The GU10 bushing shape is a widely used format in small transformerless LED spotlights. Usually used in dichroic halogen lamps.
• B22: Type of bayonet connector used in countries such as Africa, India and Ireland.
• MR16: Its use is normally limited to 12V halogen lamps.