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A switched line is a communications link established through the use of switching equipment which allows a connection to be established between two transmission devices. The switched line provides a temporary connection between two user terminals or machines and only lasts for a certain period. Switched lines minimize the line costs while maintaining the advantages of interconnected systems. They are less expensive compared to leased lines and are often appropriate when there is low traffic, as well as for connecting several remote sites.
A switched line allows a physical transmission path to be established and dedicated to a single connection between two points of a network for the duration that the connection lasts. However, the switched network does not have dedicated links between the points or users, and therefore requires extra switching hardware.
The switching equipment provides a temporary communication path between the two user terminals, giving the two users exclusive use of the link. The communication path provided by the switched line may vary each time a connection is established between two users.
Switched lines are commonly used for ordinary voice telephone systems where the telephone company reserves the established physical path between a caller and the called number. The reservation lasts throughout the call and no one else can use the associated physical lines during this time.
A switching device such as a private branch network (PBX) is often used within an organization to provide users with the ability to share a number of external phone lines directly from their extensions. The PBX allows users to access and share a few external lines, and hence eliminates the need to assign each user an individual line.
Advantages of a switched line are: