Higher data rates generally imply shorter ranges a local area network operating at millions of bits per second may only cover one floor of an office building, but eliminates the need for installation of dedicated network cabling. Low-frequency (about 100–200 kHz) carriers impressed on high-voltage transmission lines may carry one or two analog voice circuits, or telemetry and control circuits with an equivalent data rate of a few hundred bits per second however, these circuits may be many miles long. is a notable exception, permitting limited-power wide-band signals to be injected into unshielded wiring, as long as the wiring is not designed to propagate radio waves in free space.ĭata rates and distance limits vary widely over many power-line communication standards. Some jurisdictions (such as the EU), regulate wire-line transmissions further. These jurisdictions usually require unlicensed uses to be below 500 kHz or in unlicensed radio bands. Many nations regulate unshielded wired emissions as if they were radio transmitters. The main issue determining the frequencies of power-line communication is laws to limit interference with radio services. The propagation problem is a limiting factor for each type of power-line communications. Since the power distribution system was originally intended for transmission of AC power at typical frequencies of 50 or 60 Hz, power wire circuits have only a limited ability to carry higher frequencies. Different types of power-line communications use different frequency bands. Power-line communications systems operate by adding a modulated carrier signal to the wiring system. Radio interference, for example, has long been a concern of amateur radio groups. Various data rates and frequencies are used in different situations.Ī number of difficult technical problems are common between wireless and power-line communication, notably those of spread spectrum radio signals operating in a crowded environment. Typically transformers prevent propagating the signal, which requires multiple technologies to form very large networks. Most PLC technologies limit themselves to one type of wires (such as premises wiring within a single building), but some can cross between two levels (for example, both the distribution network and premises wiring). Power-line communication (also known as power-line carrier), abbreviated as PLC, carries data on a conductor that is also used simultaneously for AC electric power transmission or electric power distribution to consumers.Ī wide range of power-line communication technologies are needed for different applications, ranging from home automation to Internet access which is often called broadband over power lines (BPL). Please leave a comment below if you have any questions.For other schemes to deliver data and power over one cable, see Power over. May I recommend you print this note and check things off as you have master the topics. Know that it will take some time for the material to sink in. As the inductor is "turned off" it will act as a constant current source and do whatever is necessary to maintain the same current before and after the transition.Ĥ) Please search "transistor characteristic curves." Here you will find that a transistor appears to operate as an acceptable constant current source. Such a device would demand infinite current (again, not possible in this universe).ģ) Please search "inductor kickback." Here you will find than an inductor acts as a constant current source for a limited amount of time. Note that there is no such thing as a perfect constant voltage source. To make one you would need a device that could produce an infinite voltage (not possible).Ģ) Please search "Thevenin Norton Equivalent." Here you will find that a voltage source with series resistance can be modeled as a current source with parallel resistor. To my knowledge there are no perfect constant current sources. It will take on whatever voltage is necessary to do so including both positive and negative voltages. I'll give you a few examples to consider:ġ) The current source is a mathematical construct that maintains a constant current. The current source is a different animal. With more current and a fixed voltage there will be more power. As you stated as the resistance is decreased more current flows. Examples include a battery or wall outlet. In my opinion the voltage source is relatively straightforward. CAUTION - this is an answer from an electrical engineer.
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