1A2 Key Telephone System

The 1A2 Key Telephone System is a business telephone system developed and distributed by the Western Electric Company for the Bell System.

The 1A2 Key Telephone System was a modular system that provided flexible solutions for a variety of telephone service requirements. It provided multiple users with control over multiple telephone lines without the requirement for an operator, system attendant, or receptionist. Each user could select a specific telephone line to place calls on, or to answer calls, and manage those calls by placing them on hold or transferring them to other stations. The system provided options for station-to-station signaling and intercom, and music-on-hold. The control functions were operated directly on each telephone instrument with a set of push buttons (keys) that had lamps installed internally to provide visual indication of line status.

Introduced in 1964, the 1A2 system represents a stage of key telephone systems development at Bell Laboratories that started in the late 1930s with the 1A Key Telephone System, and was an improvement over the 1A1 system introduced in 1953.

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".