It is normally used dBm optical fiber, external radio networks, microwave. This measure, which also can be called dBmW is a measure that is in decibels relative to one milliwatt. The main idea is to measure dBm power factors.

The dBm (sometimes also dBmW or decibel-milliwatt) is a unit of measurement of power expressed in decibels (dB) relative to one milliwatt (mW). It is used in radio networks, microwave and optical fiber as a convenient measure of absolute power because of their ability to express both very large and very small values ??in short form. It is distinct from dBW, which refers to one watt (mW 1,000). Typical values:

• 21 DBM-> 125 MW> Maximum output power for a mobile phone UMTS/3G (phone power class 4).
• 15 DBM-> 32 MW> Typical power transmission WiFi laptops.
• 0 DBM-> 1.0 mW = 1000 ?W-> Standard Bluetooth Class 3 coverage 1m.
• DBM- -10> 100 ?W-> Typically the maximum Potentiometeria that can be received on a wireless network (-10 to -30 dBm).
• -194 DBM-> 0.00004 AW-> thermal noise bandwidth of 1 Hz in outer space (4 kelvin).

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