Beauchamp, Ken (2024). History of Telegraphy > 자유게시판

However, the higher voltages used in many AC electrification systems reduce transmission losses over longer distances, allowing for fewer substations or more powerful locomotives to be used. Electric vehicles, especially locomotives, lose power when traversing gaps in the supply, such as phase change gaps in overhead systems, and gaps over points in third rail systems. Whatever the causes of the sparks effect, it is well established for numerous routes that have electrified over decades. Foreshadowing today's network hubs and switches, Farallon provided solutions for PhoneNet to be used in star as well as bus configurations, with both passive star connections (with the phone wires simply bridged to each other at a central point), and active star with "PhoneNet Star Controller" hub hardware. These drives can run equally well on DC or AC of any frequency, and many modern electric locomotives are designed to handle different supply voltages and frequencies to simplify cross-border operation. The DC system, apart from being limited as to the maximum power that can be transmitted, also can be responsible for electrochemical corrosion due to stray DC currents. Although the supply has an artificially created earth point, this connection is derived by using resistors which ensures that stray earth currents are kept to manageable levels.

RF enables communication in the 868.3 MHz band for using frequency shift keying with Manchester data encoding. This use of ATP provided automatic flow control; each end could only send data to the other end if there was an outstanding ATP request to respond to. The problem was exacerbated because the return current also had a tendency to flow through nearby iron pipes forming the water and gas mains. This scheme was introduced because of the problems of return currents, intended to be carried by the earthed (grounded) running rail, flowing through the iron tunnel linings instead. Since the tyres do not conduct the return current, the two guide bars provided outside the running 'roll ways' become, in a sense, a third and fourth rail which each provide 750 V DC, so at least electrically it is a four-rail system. The trains move on rubber tyres which roll on a pair of narrow roll ways made of steel and, in some places, of concrete. Power-only rails can be mounted on strongly insulating ceramic chairs to minimise current leak, but this is not possible for running rails, which have to be seated on stronger metal chairs to carry the weight of trains.

This is partly offset by the weight of electrical equipment. For passenger operation it is possible to provide enough power with diesel engines (see e.g. 'ICE TD') but, at higher speeds, this proves costly and impractical. It’s that, in the short run, you take a big hit but, in the long run, you get respect. The lines were connected at both ends to revolving dials marked with the letters of the alphabet and electrical impulses sent along the wire were used to transmit messages. The requestor then sent an acknowledgement packet containing a bit mask indicating which of the response packets it received, so the responder could retransmit the remainder. Well, if you plugged a delay directly into your amp’s input then it would sound fairly out of control, especially through the distortion channel. The standard-frequency AC system may introduce imbalance to the supply grid, requiring careful planning and design (as at each substation power is drawn from two out of three phases). By using this process, any node that transmits a logical 1, when another node transmits a logical 0, loses the arbitration and drops out. The Germans developed a highly complex teleprinter attachment (German: Schlüssel-Zusatz, "cipher attachment") that was used for enciphering telegrams, using the Lorenz cipher, between German High Command (OKW) and the army groups in the field.

Large fossil fuel power stations operate at high efficiency, and can be used for district heating or to produce district cooling, leading to a higher total efficiency. Central station electricity can often be generated with higher efficiency than a mobile engine/generator. Electricity for electric rail systems can also come from renewable energy, nuclear power, or other low-carbon sources, which do not emit pollution or emissions. An early advantage of AC is that the power-wasting resistors used in DC locomotives for speed control were not needed in an AC locomotive: multiple taps on the transformer can supply a range of voltages. Separate low-voltage transformer windings supply lighting and the motors driving auxiliary machinery. Also, in the de facto mechanical configuration mentioned above, what is control cable a supply rail is included to distribute power to each of the transceiver nodes. The use of AC is usually not feasible due to the dimensions of a third rail being physically very large compared with the skin depth that AC penetrates to 0.3 millimetres or 0.012 inches in a steel rail.