Explain Time Switching.

Time Switches: The principle of a time switch is demonstrated in figure. This connects an incoming n channel PCM highway to an outgoing n channel PCM highway. As any incoming channel can be connected to one outgoing channel, this is corresponding to space division cross point matrix along with n incoming and n outgoing trunks, as demonstrated in figure. Time-slot interchange is carried out through two stores, each containing a storage address for each channel of the PCM frame. The speech store consists of each data of the incoming time-slots (that is its speech sample) at a matching address. All address of the connection store corresponds to a time slot upon the outgoing highway. This contains the number of the time-slot on the incoming highways that sample is to be transmitted in which outgoing time-slots. Information is read in the speech store cyclically in synchronism with the incoming PCM systems; however, random access read out is utilized .The connection store has cyclic read out, although writing in is non cyclic. To set up a connection, the number (X of the time-slot of an incoming channel is written in the connection store at the address equivalent to the selected outgoing channel (Y ).Throughout each cyclic scan of the speech store ,the incoming PCM sample from channel X is written in address X. Throughout each cyclic scan of the connection store, the number X is read out at the starting of time-slot Y. It is decoded to select address X of the speech store, which contents are read out and sent over the outgoing highway.

FIG - Time Switch