At any point in a transmission system, the ratio of the circuit noise at that point to an arbitrary level chosen as a reference.
Note: The circuit noise level is usually expressed in dBrn0, signifying the reading of a circuit noise meter, or in dBa0, signifying circuit noise meter reading adjusted to represent an interfering effect under specified conditions.

The percentage of time a circuit was available for use in a specified period of scheduled availability.
Note 1: Circuit reliability is given by where To is the circuit total outage time, Ts is the circuit total scheduled time, and Ta is the circuit total available time.
Note 2: Ts = Ta + To. Synonym time availability.

The process by which a communications circuit is established between two users after disruption or loss of the original circuit.
Note: Circuit restoration is usually performed in accordance with planned procedures and priorities. Restoration may be effected automatically, e.g., by switching to a hot standby, or manually, e.g., by manual patching.

In open systems architecture, the logical path of a message in a communications network based on a series of gates at the physical network layer in the Open Systems Interconnection--Reference Model and the GOSIP FIPS PUB 146-1.

1. A method of routing traffic through a switching center, from local users or from other switching centers, whereby a connection is established between the calling and called stations until the connection is released by the called or calling station.
2. A process that, on demand, connects two or more data terminal equipments (DTEs) and permits the exclusive use of… (Read More →)

See circuit switching, switching center.

Equipment used for routing messages over common-user circuits that interconnect a source data terminal equipment (DTE) to a sink DTE for information interchange.

In ISDN applications, a transfer mode by means of permanent allocation of channels or bandwidth between connections.

A data transmission service requiring the establishment of a circuit-switched connection before data can be transferred from source data terminal equipment (DTE) to a sink DTE.
Note: A circuit-switched data transmission service uses a connection-oriented network.

In electromagnetic wave propagation, polarization such that the tip of the electric field vector describes a helix.
Note 1: The magnitude of the electric field vector is constant.
Note 2: The projection of the tip of the electric field vector upon any fixed plane intersecting, and normal to, the direction of propagation, describes a circle.
Note 3: A circularly polarized… (Read More →)