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Electric trains need not carry the weight of prime movers, transmission and fuel. This is partly offset by the weight of electrical equipment. These systems could either use standard network frequency and three power cables, or reduced frequency, which allowed for return-phase line to be third rail, rather than an additional overhead wire. Such installations are in the Western Dedicated Freight Corridor in India where the wire height is at 7.45 m (24.4 ft) to accommodate double-stack container trains without the need of well-wagons. Multiple access on CAN bus is achieved by the electrical logic of the system supporting just two states that are conceptually analogous to a ‘wired AND’ network. However, "broadband video" in the context of streaming Internet video has come to mean video files that have bit-rates high enough to require broadband Internet access for viewing. 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.

In theory, these trains could enjoy dramatic savings through electrification, but it can be too costly to extend electrification to isolated areas, and unless an entire network is electrified, companies often find that they need to continue use of diesel trains even if sections are electrified. A parallel port makes this simpler; the entire ASCII value is presented on the pins in complete form. The older parallel printer ports had an 8-bit data bus and four pins for control output (Strobe, Linefeed, Initialize, and Select In), and five more for control input (ACK, Busy, Select, Error, and Paper Out). We’ve got the hollowing out of industry: we now don’t have the skills. The converters turned out to be unreliable and the experiment was curtailed. 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. 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.

Third rail is more compact than overhead wires and can be used in smaller-diameter tunnels, an important factor for subway systems. Network effects are a large factor with electrification. Most electrification systems use overhead wires, but third rail is an option up to 1,500 V. Third rail systems almost exclusively use DC distribution. In contrast, low-speed CAN 2.0 supports bit rates from 40 kbit/s to 125 kbit/s and offers fault tolerance by allowing communication to continue despite a fault in one of the two wires, with each node maintaining its own termination. The lower current reduces line loss, thus allowing higher power to be delivered. 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. Regenerative braking returns power to the electrification system so that it may be used elsewhere, by other trains on the same system or returned to the general power grid. This is less of a problem in trains consisting of two or more multiple units coupled together, since in that case if the train stops with one collector in a dead gap, another multiple unit can push or pull the disconnected unit until it can again draw power.

The return of each traction motor, as well as each wagon, is effected by one contact shoe each that slide on top of each one of the running rails. Whatever the causes of the sparks effect, it is well established for numerous routes that have electrified over decades. Some electrifications have subsequently been removed because of the through traffic to non-electrified lines. A few lines of the Paris Métro in France operate on a four-rail power system. The key advantage of the four-rail system is that neither running rail carries any current. Each wheel set of a powered bogie carries one traction motor. If the local times of two places differ by one hour, the difference in longitude between them is 15° (360°/24h). Before telegraphy, absolute time could be obtained from astronomical events, such as eclipses, occultations or lunar distances, or by transporting an accurate clock (a chronometer) from one location to the other. Considered to be one of the most basic external connections to a computer, the serial port has been an integral part of most computers for more than 20 years. Years later, in 1987, IBM reintroduced the bidirectional interface with its IBM PS/2 series, where it could be enabled or disabled for compatibility with applications hardwired not to expect a printer port to be bidirectional.

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