Common control
Encyclopedia
In telecommunication
, a common control is an automatic telephone exchange
arrangement in which the control equipment necessary for the establishment of connections is shared by being associated with a given call
only during the period required to accomplish the control function for the given call. The first examples deployed on a major scale were the Director telephone system
in London and the panel switch
in the Bell System
. Direct control telephone exchange
s became rare in the 1960s, leaving only common control ones.
Note: During the 1980s, common control exchanges became stored program control exchange
s, using common channel signaling
in which the channels that are used for signaling, whether frequency
bands or time
slots, are not used for message
traffic
.
Telecommunication
Telecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded...
, a common control is an automatic telephone exchange
Telephone exchange
In the field of telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls...
arrangement in which the control equipment necessary for the establishment of connections is shared by being associated with a given call
Telephone call
A telephone call is a connection over a telephone network between the calling party and the called party.-Information transmission:A telephone call may carry ordinary voice transmission using a telephone, data transmission when the calling party and called party are using modems, or facsimile...
only during the period required to accomplish the control function for the given call. The first examples deployed on a major scale were the Director telephone system
Director telephone system
The Director System was a system which made it possible to call subscribers at other telephone exchanges without operator intervention in large multi-exchange cities, and to have a mixture of automatic and manual exchanges within these cities...
in London and the panel switch
Panel switch
The panel switching system was an early type of automatic telephone exchange, first put into urban service by the Bell System in the 1920s and removed during the 1970s...
in the Bell System
Bell System
The Bell System was the American Bell Telephone Company and then, subsequently, AT&T led system which provided telephone services to much of the United States and Canada from 1877 to 1984, at various times as a monopoly. In 1984, the company was broken up into separate companies, by a U.S...
. Direct control telephone exchange
Telephone exchange
In the field of telecommunications, a telephone exchange or telephone switch is a system of electronic components that connects telephone calls...
s became rare in the 1960s, leaving only common control ones.
Note: During the 1980s, common control exchanges became stored program control exchange
Stored Program Control exchange
Stored Program Control exchange is the technical name used for telephone exchanges controlled by a computer program stored in the memory of the system. Early exchanges such as Strowger, panel, rotary, and crossbar switches were electromechanical and had no software control...
s, using common channel signaling
Common Channel Signaling
In telephony, Common Channel Signaling , in the US also Common Channel Interoffice Signaling , is the transmission of signaling information on a separate channel from the data, and, more specifically, where that signaling channel controls multiple data channels.For example, in the public switched...
in which the channels that are used for signaling, whether frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
bands or time
Time
Time is a part of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify rates of change such as the motions of objects....
slots, are not used for message
Message
A message in its most general meaning is an object of communication. It is a vessel which provides information. Yet, it can also be this information. Therefore, its meaning is dependent upon the context in which it is used; the term may apply to both the information and its form...
traffic
Traffic
Traffic on roads may consist of pedestrians, ridden or herded animals, vehicles, streetcars and other conveyances, either singly or together, while using the public way for purposes of travel...
.