When the number of inlets is equal to the number of outlets for a switching network, such a network is called the Symmetric Network, which means N=M. A network where the outlets are connected to the inlets, is called the Folded Network.

In a Folded Network, the N number of inlets which come as outlets are again folded back to the inlets. Nevertheless, the switching network provides connections to the inlets and outlets as per the requirement. The following figure will help you understand how the Switching Network works.

As one connection can be given to one line per time, only N/2 connections are established for N inlets of a folded network. Such a network can be called as Non-blocking network. In a non-blocking network, as long as the called subscriber is free, a calling subscriber will be able to establish a connection to the called subscriber.

In the above figure, only 4 subscribers were considered – where line 1 is busy with line 2 and line 3 is busy with line 4. While the call is in progress, there used to be no chance for making another call and hence, only a single connection was made. Hence for N inlets, only N/2 lines are connected.

At times, it might happen that the inlet and outlet connections are continuously used to make Transit calls through trunk lines only, but not among the local subscribers. The inlet and outlet connections if used in an Inter-exchange transmission such that the exchange does not support connection between local subscribers, then it is called the Transit Exchange. A switching network of such kind is called the Non-folded network. This is shown in the following figure −