Explain Space Switching.

Space Switches: Connections can be made in between outgoing and incoming PCM highways by a cross point matrix of the form demonstrated in figure. However, various channels of an incoming PCM frame may require to be switched by various cross points in order to reach various destinations. Therefore, the cross point is a two-input AND gate. One input is linked to the incoming PCM highway and another to a connection store which produce a pulse at the needed instant. A group of cross points gates can be implemented like an integrated circuit, for illustration using a multiplexer chip.

FIG - Space Switch.

Figure demonstrates a space switch with k incoming and m outgoing PCM highways, all carrying n channels. The connections store for every column of cross points is a memory along with an address location for every time-slot that stores the number of the cross points to be operated in which time slot. This number is written in the address by the controlling processor so as to setup the connection. The numbers are read out cyclically, into synchronism along with the incoming PCM frame. In every time slot, the number stored at the equivalent store address is read out and decoding logic converts it in a pulse or a single lead to function the relevant cross point.

Because a cross point can make a diverse connection in each of the n time-slots, this is corresponding to n cross points in a space division network. The total space switch is therefore equivalent to n separate k x m switches in a space division switching network.