Concept of Circuit

round-arrowThe word “circuit” is derived from the Latin word “circuitus” meaning circular motion, cycle, to go round, circle etc. “circuit” as a noun has the following meanings:

  • a circular journey or one beginning and ending at the same place; a round.
  • the route followed, places visited, or district covered by such a journey.
  • the line going around or bounding any area or object; the distance about an area or object.

Let's Explore Science... Turn on the Light

An electric circuit is a path in which electrons from a voltage or current source flow. The reason for the path to be called a circuit is that the electric current (charge in motion) flow in a closed path.

The point where those electrons enter an electrical circuit is called the “source” of electrons. The point where the electrons leave an electrical circuit is called the “return” or “earth ground“. The exit point is called the “return” because electrons always end up at the source when they complete the path of an electrical circuit.

LED-electronic_circuitAn electronic circuit is composed of individual electronic components, such as resistors, transistors, capacitors, inductors and diodes, connected by conductive wires or traces through which electric current can flow.


boolean circuitIn theoretical computer science, a circuit is a model of computation in which input values proceed through a sequence of gates, each of which computes a function. Circuits of this kind provide a generalization of Boolean circuits and a mathematical model for digital logic circuits. Circuits are defined by the gates they contain and the values the gates can produce. For example, the values in a Boolean circuit are boolean values, and the circuit includes conjunction (Logical AND), disjunction (Logical OR), and negation gates. The values in an integer circuit are sets of integers and the gates compute set union, set intersection, and set complement, as well as the arithmetic operations addition and multiplication.

telecomm circuit switching

A telecommunication circuit is any line, conductor, or other conduit (pipe) by which information is transmitted.



Telecommunication circuit is of two types.

  1. Dedicated circuit : It’s a line that’s dedicated to only one use. Meaning, the connection path is occupied by the conversation that’s happening between the source and the destination. Throughout the length of the conversation no other traffic will occupy the circuit. Dedicated circuit is also known as private circuit or leased line. Common example is analog telephone calls.
  2. Switched circuit : It’s the opposite of dedicated circuit  which is composed of different paths. Focus on the word “switch”; the communication path can change during the conversation. Examples include digital telephone (ISDN) line because the circuit can connect to any other telephone number.

I want to go deep about switched circuit.

Switched circuit => Switched commn. path => Commn. path is being switched => Commn. path is altered/changed. A visual analogy of switching is the change of tracks on a railway. The track gets switched altering the course of train.

Railway track switching

To me this railway track analogy hits the nail on the head and helps to understand every time when the word “switching” appears in any context.

Traditionally, Telecommunications deals with voice whereas Data networks deals with the data. A dedicated circuit to telecommunications is what a switched circuit to data networks. Data networks’ technology has its roots in telecommunications and it’s always ideal to understand the networking concepts by contrasting them with telecommunications work flow.

About Deepak Devanand

Seeker of knowledge
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