A telecommunication circuit is any line, conductor, or other conduit by which information is transmitted.
A dedicated circuit, private circuit, or leased line is a line that is dedicated to only one use. Originally, this was analog, and was often used by radio stations as a studio/transmitter link (STL) or remote pickup unit (RPU) for their audio, sometimes as a backup to other means. Later lines were digital, and used for private corporate data networks.
The opposite of a dedicated circuit is a switched circuit, which can be connected to different paths. A POTS or ISDN telephone line is a switched circuit, because it can connect to any other telephone number.
On digital lines, a virtual circuit can be created to serve either purpose, while sharing a single physical circuit.
Telecommunication circuit Wikipedia
A telecommunication circuit may be defined as follows:The complete path between two terminals over which one-way or two-way communications may be provided. See communications protocol.
An electronic path between two or more points, capable of providing a number of channels.
A number of conductors connected for the purpose of carrying an electric current.
An electronic closed-loop path among two or more points used for signal transfer.
A number of electrical components, such as resistors, inductances, capacitors, transistors, and power sources connected in one or more closed loops.