Remote feed

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From remote powering one speaks in electrical engineering when a connected via signal line system component is supplied through its signal line with energy.

This makes use of the fact that alternating and direct voltages are superimposed on one another, transmitted together and technically easy to separate from one another. The direct voltage fed in for the energy supply therefore has no influence on the useful signal transmitted as alternating voltage.

Since signal lines usually do not have large cross-sections, the power that can be transmitted is limited. Therefore, devices with a low power requirement are preferably fed remotely. Typical examples are signal amplifiers, LNBs , measuring or communication devices.

The term phantom power is often used synonymously with "remote power", but this is usually wrong. Phantom power is a special type of remote power supply in professional sound technology , which in terms of circuitry is dependent on the cables that are common there (two signal wires and shielding).

Application examples

Computer technology

With Power over Ethernet technology (PoE), for example, WLAN access points and VoIP telephones can be supplied with power via the data wires.

High frequency technology

In order to be able to install antenna signal amplifiers at technically favorable, often exposed points, they are supplied with energy via the antenna cable. Examples: car antenna on the car roof, cable TV amplifier in the basement, satellite antenna on the roof. The supply can either be provided by the receiving device itself or by an intermediate remote supply device. Separate feed elements are referred to as bias tees based on the internal circuit.

Communications engineering

In the case of analog telephones, the terminal is (remotely) powered by the exchange via the two speech wires ; Cordless phones and modems do not use it. This distinguishes them from local battery- powered, very old telephones and field telephones , the clearest distinguishing feature of which is the crank inductor for generating the alternating ring voltage .

In the case of ISDN subscriber connections, the line termination ( NTBA ) and possibly also a terminal device are supplied with energy via the telephone line (100 volts direct voltage).

Sound engineering

A condenser microphone always contains an amplifier that needs to be supplied with energy. Instead of a battery in the microphone, phantom power or tone wire power can be used.

The microphone connection of a computer or a sound card provides a supply voltage sufficient for electret microphones .


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