Business telephone system

A business telephone system is a multiline telephone system typically used in business environments, encompassing systems ranging from small key telephone systems to large-scale private branch exchanges.

A business telephone system differs from an installation of several telephones with multiple central office (CO) lines in that the CO lines used are directly controllable in key telephone systems from multiple telephone stations, and that such a system often provides additional features related to call handling. Business telephone systems are often broadly classified into key telephone systems, and private branch exchanges, but many hybrid systems exist.

A key telephone system was originally distinguished from a private branch exchange (PBX) in that it did not require an operator or attendant at the switchboard to establish connections between the central office trunks and stations, or between stations. Technologically, private branch exchanges share lineage with central office telephone systems, and in larger or more complex systems, may rival a central office system in capacity and features. With a key telephone system, a station user could control the connections directly using line buttons, which indicated the status of lines with built-in lamps.

Computer case

A computer case also known as a computer chassis, tower, system unit, cabinet, base unit or simply case and sometimes incorrectly referred to as the "CPU" or "hard drive", is the enclosure that contains most of the components of a computer (usually excluding the display, keyboard and mouse).

Cases are usually constructed from steel (often SECC — Steel, electrogalvanized, cold-rolled, coil) or aluminium. Plastic is sometimes used, and other materials such as glass, wood and even Lego blocks have appeared in home-built cases.

Sizes

Cases can come in many different sizes (known as form factors). The size and shape of a computer case is usually determined by the form factor of the motherboard, since it is the largest component of most computers. Consequently, personal computer form factors typically specify only the internal dimensions and layout of the case. Form factors for rack-mounted and blade servers may include precise external dimensions as well, since these cases must themselves fit in specific enclosures.

Key system

Key System may refer to:

KeY

The KeY tool is used in formal verification of Java programs. It accepts specifications written in the Java Modeling Language to Java source files. These are transformed into theorems of dynamic logic and then compared against program semantics that are likewise defined in terms of dynamic logic. KeY is significantly powerful in that it supports both interactive (i.e. by hand) and fully automated correctness proofs. Failed proof attempts can be used for a more efficient debugging or verification-based testing. There have been several extensions to KeY in order to apply it to the verification of C programs or hybrid systems. KeY is jointly developed by Karlsruhe Institute of Technology, Germany; Technische Universität Darmstadt, Germany; and Chalmers University of Technology in Gothenburg, Sweden and is licensed under the GPL.

Overview

The usual user input to KeY consists of a Java source file with annotations in JML. Both are translated to KeY's internal representation, dynamic logic. From the given specifications, several proof obligations arise which are to be discharged, i.e. a proof has to be found. To this ends, the program is symbolically executed with the resulting changes to program variables stored in so-called updates. Once the program has been processed completely, there remains a first-order logic proof obligation. At the heart of the KeY system lies a first-order theorem prover based on sequent calculus, which is used to close the proof. Interference rules are captured in so called taclets which consist of an own simple language to describe changes to a sequent.

Key System

The Key System (or Key Route) was a privately owned company that provided mass transit in the cities of Oakland, Berkeley, Alameda,Emeryville, Piedmont, San Leandro, Richmond, Albany and El Cerrito in the eastern San Francisco Bay Area from 1903 until 1960, when it was sold to a newly formed public agency, AC Transit. The Key System consisted of local streetcar and bus lines in the East Bay, and commuter rail and bus lines connecting the East Bay to San Francisco by a ferry pier on San Francisco Bay, later via the lower deck of the Bay Bridge. At its height during the 1940s, the Key System had over 66 miles (106 km) of track. The local streetcars were discontinued in 1948 and the commuter trains to San Francisco were discontinued in 1958. The Key System's territory is today served by BART and AC Transit bus service.

History

Early years

The system was a consolidation of several streetcar lines assembled in the late 1890s and early 1900s by Francis Marion "Borax" Smith, an entrepreneur who made a fortune in his namesake mineral, and then turned to real estate and electric traction. The Key System began as the San Francisco, Oakland, and San Jose Railway (SFOSJR), incorporated in 1902. Service began on October 26, 1903 with a 4-car train carrying 250 passengers, departing downtown Berkeley for the ferry pier. Before the end of 1903, the general manager of the SFOSJR devised the idea of using a stylized map on which the system's routes resembled an old-fashioned key, with three "handle loops" that covered the cities of Berkeley, Piedmont (initially, "Claremont" shared the Piedmont loop) and Oakland, and a "shaft" in the form of the Key pier, the "teeth" representing the ferry berths at the end of the pier. The company touted its 'key route', which led to the adoption of the name "Key System".