Also found in: Dictionary, Thesaurus, Medical, Legal, Acronyms, Idioms, Wikipedia.
bus[Lat. omnibus=for all], large public conveyance. A horse-drawn urban omnibus was introduced in Paris in 1662 by Blaise Pascal and his associates, but it remained in operation for only a few years. The omnibus reappeared c.1812 in Bordeaux, France, and afterward in Paris (c.1827), London (1829), and New York City (1830). It often carried passengers both inside and on the roof. Buses were motorized early in the 20th cent.; motorbus transportation increased rapidly and is now used in most countries. A number of railroad companies operate subsidiary bus lines. A network of bus lines links all parts of the United States; many small cities and towns which have lost rail service in recent years are served only by bus lines. Buses are powered usually by gasoline or diesel engines, but in a few cities electric motors fed from overhead wires are used. The construction of small buses is similar to that of heavy automobiles, while the construction of large buses is similar to that of heavy trucks. Some large cities now use articulated buses, which can seat more than 60 passengers; such buses are constructed in two parts and joined, or articulated, with an accordian–style sleeve.
a public motor vehicle intended for carrying nine or more passengers. The first buses appeared at the beginning of the 20th century and by World War I were already in comparatively wide use. Regular bus transit routes in Moscow were inaugurated in 1924.
Buses are classified according to their service as urban, suburban, intercity (tourist), local, and general purpose. Urban buses have a passenger area with several doors for entry and exit, a limited seating capacity, a wide central aisle, and spacious “collector” platforms near the doors. Urban buses are capable of quick acceleration, which ensures a comparatively high average speed despite frequent stops. Suburban buses have a smaller center aisle and collector platforms, resulting in a greater seating capacity. In the passenger area of intercity (tourist) buses, hard or soft (sleeping) seats are installed. Equipped with heaters and ventilators, some of these buses also have a cloakroom, refrigerator, and rest room. The luggage space is located beneath the floor of the passenger area. The design of such buses must provide for high-speed travel. Local buses are used for carrying passengers along regional and interregional routes, primarily in rural areas. These buses are provided with strengthened bodies and working parts, with increased road clearance, and sometimes with drives on two or three axles.
The capacity of the bus depends on its overall dimensions, primarily its length. The length classifications accepted in the USSR are 5 meters, very small; 7.5 meters, small; 8.5 and 9.5 meters, medium; 11 meters, large; 12 meters, very large; and 16.5 meters, articulated. A variation of plus or minus 0.5 meters in length is permitted in design. Articulated buses consist of two sections, connected by flexible joints, which have a common passenger compartment. Double-decker and split-level buses have found some use in urban transportation abroad. The capacity of 7.5–meter buses varies from 35 to 40 people and of 12–meter buses from 110 to 120 people. Articulated buses can accomodate up to 160 people. The lower limit of maximum speed is established according to the buses’ classifications: 70 km/hr for urban, 80 km/hr for suburban and local, and 100 km/hr for intercity. Operating requirements also dictate that, depending on classification and length, the acceleration time from zero to the indicated maximum speed must not exceed 40–55 seconds for urban, 50–65 seconds for suburban, and 70–90 seconds for intercity buses (see Table 1).
|Table 1. Technical characteristics of some bus models in use in the USSR|
|Bus||Overall length (meters)||seated||total at peak hour||Maximum speed (km/hr)||kilowatts||horsepower||Fuel consumption (liters/100 km)|
|* Articulated bus|
|lkarus-180* (Hungary) ....||16.5||35||119(172)||67||147||200||24.4|
The body may be of truck or coach type, the latter being more prevalent. The coach body usually serves as the load-bearing structure on which the engine, transmission box, and front and rear axles are mounted.
The engine may be mounted in front, in the center under the floor of the passenger area, or in the rear. The drive is usually through the rear axle. Some very high-maneuverability buses have four-wheel drive.
Automatic transmissions are being more frequently installed in urban and suburban buses. Buses with conventional transmissions and engines mounted centrally or in the rear employ remote control of the clutch and transmission. Buses are beginning to be equipped with compressed-air suspensions using rubber-ply bellows which, in addition to a smoother ride, help maintain an even floor and footboard level regardless of load. Medium and large buses are equipped with power steering, which substantially reduces the force required to turn the steering wheel. The foot brake mechanism to the front and rear axles of medium and large buses is pneumatic or air-over-hydraulic; the axles as a rule have separate systems. Very small buses are equipped with hydraulic brakes; small buses have compressed-air or vacuum-boosted hydraulic brakes. Some buses, especially intercity ones, employ decelerator brakes.
REFERENCESPlekhanov, I. P. Tekhniko-ekspluatatsionnye trebovaniia k avtobusam. Moscow, 1967.
Kratkii avtomobil’nyi spravochnik. Moscow, 1968.
(bus bar), a copper, aluminum, or, less often, steel electrical conductor, usually rectangular or circular in cross section, used to handle large currents, for example, in switchgear.
What does it mean when you dream about a bus?
Because of our early experiences with school buses, as well as the widespread availability of buses as public transportation, buses can have a wide variety of individual associations. Also, buses may simply be stages for other kinds of dream scenarios (i.e., they do not necessarily have a symbolic meaning). In and of themselves, and especially in contrast to more individualized means of transportation such as automobiles, buses may represent collective action, or even going along with the crowd.
The width of the data bus, i.e. the number of parallel connectors, and its clock rate determine its data rate (the number of bytes per second which it can carry). This is one of the factors limiting a computer's performance. Most current microprocessors have 32-bit busses both internally and externally. 100 or 133 megahertz bus clock rates are common. The bus clock is typically slower than the processor clock.
Some processors have internal busses which are wider than their external busses (usually twice the width) since the width of the internal bus affects the speed of all operations and has less effect on the overall system cost than the width of the external bus.
Various bus designs have been used in the PC, including ISA, EISA, Micro Channel, VL-bus and PCI. Other peripheral busses are NuBus, TURBOchannel, VMEbus, MULTIBUS and STD bus.
Some networks are implemented as a bus at the physical layer, e.g. Ethernet - a one-bit bus operating at 10 (or later 100) megabits per second.
The term is almost certainly derived from the electrical engineering term "bus bar" - a substantial, rigid power supply conductor to which several connections are made. This was once written "'bus bar" as it was a contraction of "omnibus bar" - a connection bar "for all", by analogy with the passenger omnibus - a conveyance "for all".
More on derivation.
busA shared digital pathway between resources and devices. In a computer, there are two major types: the system bus and peripheral bus. The system bus, also known as the "frontside bus" or "local bus," is the internal path from the CPU to memory and is split into address bus and data bus subsets. Addresses are sent over the address lines to signal a memory location, and data are transferred over the data lines to that location.
System buses transfer data in parallel. In a 32-bit bus, data are sent over 32 wires simultaneously. A 64-bit bus uses 64 wires.
The peripheral bus is the pathway to the peripheral devices such as a disk or printer. PCI and PCI Express are widely used peripheral buses. Devices connect to these parallel buses with cables to controller cards that plug into slots on the motherboard. Another common bus is USB, and devices are cabled to ports on the computer. USB is a serial bus, in which data travels over one wire.
Other peripheral buses have been used, including ISA, EISA, Micro Channel, VL-bus, NuBus, TURBOchannel, VMEbus, MULTIBUS and STD bus. The CAN bus and FlexRay bus are automotive buses.
Why Is It Called a Bus?
Inaccurate naming. Electronic buses are shared pathways, in which all devices receive the same signals. They do not function like a passenger bus that makes prescribed stops, one after the other. The data transfer technology similar to a passenger bus is a ring network (see Token Ring). See bus network, software bus, serial bus, PCI, PCI Express, USB and AGP.
|System and Peripheral Buses|
|This illustration shows how chips, memory and peripherals in a PC interconnect via the system bus (top) and peripheral buses (AGP, PCI and PCI Express).|